tag:theconversation.com,2011:/id/topics/ice-melt-5285/articlesIce melt – The Conversation2023-07-27T20:11:18Ztag:theconversation.com,2011:article/2097952023-07-27T20:11:18Z2023-07-27T20:11:18ZAncient pathogens released from melting ice could wreak havoc on the world, new analysis reveals<figure><img src="https://images.theconversation.com/files/539710/original/file-20230727-23-jtkhdm.jpeg?ixlib=rb-1.1.0&rect=0%2C66%2C4025%2C2565&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Science fiction is rife with fanciful tales of deadly organisms emerging from the ice and wreaking havoc on unsuspecting human victims. </p>
<p>From <a href="https://www.imdb.com/title/tt0084787/">shape-shifting aliens</a> in Antarctica, to super-parasites emerging from a <a href="https://www.imdb.com/title/tt1235448/">thawing woolly mammoth</a> in Siberia, to exposed <a href="https://www.nytimes.com/2021/05/20/books/review/jim-shepard-phase-six.html">permafrost in Greenland</a> causing a viral pandemic – the concept is marvellous plot fodder.</p>
<p>But just how far-fetched is it? Could pathogens that were once common on Earth – but frozen for millennia in glaciers, ice caps and <a href="https://climate.mit.edu/explainers/permafrost">permafrost</a> – emerge from the melting ice to lay waste to modern ecosystems? The potential is, in fact, quite real. </p>
<h2>Dangers lying in wait</h2>
<p>In 2003, <a href="https://ami-journals.onlinelibrary.wiley.com/doi/abs/10.1046/j.1462-2920.2003.00422.x">bacteria were revived</a> from samples taken from the bottom of an ice core drilled into an <a href="https://byrd.osu.edu/research/groups/ice-core-paleoclimatology/projects/china/guliya">ice cap</a> on the <a href="https://goo.gl/maps/zjN3NVk8TAb6GrxZ9">Qinghai-Tibetan plateau</a>. The ice at that depth was more than 750,000 years old. </p>
<p>In 2014, a giant “zombie” <em>Pithovirus sibericum</em> virus was <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1320670111">revived from</a> 30,000-year-old Siberian permafrost.</p>
<p>And in 2016, an outbreak of <a href="https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/anthrax">anthrax</a> (a disease caused by the bacterium <em>Bacillus anthracis</em>) <a href="https://goo.gl/maps/fjV8u2mRbbC7UoAs5">in western Siberia</a> was attributed to the rapid <a href="https://link.springer.com/article/10.1007/s10393-021-01549-5">thawing of <em>B. anthracis</em> spores</a> in permafrost. It killed thousands of reindeer and affected dozens of people.</p>
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<img alt="" src="https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=395&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=395&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=395&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=496&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=496&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537599/original/file-20230716-126451-ymm8xc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=496&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Bacillus anthracis</em> is a soil bacterium that causes anthrax.</span>
<span class="attribution"><span class="source">William A. Clark/USCDCP</span></span>
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</figure>
<p>More recently, scientists found <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1073">remarkable genetic compatibility</a> between viruses isolated from lake sediments in the high Arctic and potential living hosts.</p>
<p>Earth’s climate is warming at a <a href="https://theconversation.com/it-can-be-done-it-must-be-done-ipcc-delivers-definitive-report-on-climate-change-and-where-to-now-201763">spectacular rate</a>, and up to four times faster <a href="https://www.nature.com/articles/s43247-022-00498-3">in colder regions</a> such as the Arctic. Estimates suggest we can expect <a href="https://ami-journals.onlinelibrary.wiley.com/doi/10.1111/j.1462-2920.2012.02876.x">four sextillion</a> (4,000,000,000,000,000,000,000) microorganisms to be released from ice melt each year. This is about the same as the estimated number of stars <a href="https://www.esa.int/Science_Exploration/Space_Science/Herschel/How_many_stars_are_there_in_the_Universe">in the universe</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/for-110-years-climate-change-has-been-in-the-news-are-we-finally-ready-to-listen-188646">For 110 years, climate change has been in the news. Are we finally ready to listen?</a>
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<p>However, despite the unfathomably large number of microorganisms being released from melting ice (including pathogens that can potentially infect modern species), no one has been able to estimate the risk this poses to modern ecosystems.</p>
<p>In <a href="http://doi.org/10.1371/journal.pcbi.1011268">a new study</a> published today in the journal PLOS Computational Biology, we calculated the ecological risks posed by the release of unpredictable ancient viruses.</p>
<p>Our simulations show that 1% of simulated releases of just one dormant pathogen could cause major environmental damage and the widespread loss of host organisms around the world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537499/original/file-20230714-15-iyqll0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Melt water carving a glacier in the Himalayas of India.</span>
<span class="attribution"><span class="source">Sharada Prasad</span></span>
</figcaption>
</figure>
<h2>Digital worlds</h2>
<p>We used a software called <a href="https://alife.org/encyclopedia/digital-evolution/avida/">Avida</a> to run experiments that simulated the release of one type of ancient pathogen into modern biological communities. </p>
<p>We then measured the impacts of this invading pathogen on the diversity of modern host bacteria in thousands of simulations, and compared these to simulations where no invasion occurred.</p>
<p>The invading pathogens often survived and evolved in the simulated modern world. About 3% of the time the pathogen became dominant in the new environment, in which case they were very likely to cause losses to modern host diversity. </p>
<p>In the worst- (but still entirely plausible) case scenario, the invasion reduced the size of its host community by 30% when compared to controls.</p>
<p>The risk from this small fraction of pathogens might seem small, but keep in mind these are the results of releasing just one particular pathogen in simulated environments. With the sheer number of ancient microbes being released in the real world, such outbreaks represent a substantial danger.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/melting-ice-leaves-polar-ecosystems-out-in-the-sun-19807">Melting ice leaves polar ecosystems out in the sun</a>
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</em>
</p>
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<h2>Extinction and disease</h2>
<p>Our findings suggest this unpredictable threat which has so far been confined to science fiction could become a powerful driver of ecological change. </p>
<p>While we didn’t model the potential risk to humans, the fact that “time-travelling” pathogens could become established and severely degrade a host community is already worrisome.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/537596/original/file-20230716-122897-5fkiun.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Drilling ice cores in Greenland.</span>
<span class="attribution"><span class="source">Helle Astrid Kjær</span></span>
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</figure>
<p>We highlight yet another source of potential species extinction in the modern era – one which even our <a href="https://theconversation.com/children-born-today-will-see-literally-thousands-of-animals-disappear-in-their-lifetime-as-global-food-webs-collapse-196286">worst-case extinction models</a> do not include. As a society, we need to understand the potential risks so we can prepare for them.</p>
<p>Notable viruses such as <a href="https://www.sciencedirect.com/science/article/pii/S0092867421009910">SARS-CoV-2</a>, <a href="https://www.science.org/doi/full/10.1126/science.1259657">Ebola</a> and <a href="https://perspectivesinmedicine.cshlp.org/content/1/1/a006841">HIV</a> were likely transmitted to humans via contact with other animal hosts. So it is <a href="https://www.huffpost.com/entry/ice-caps-melt-prehistoric_b_9805334">plausible</a> that a once ice-bound virus could enter the human population via a <a href="https://theconversation.com/how-do-viruses-mutate-and-jump-species-and-why-are-spillovers-becoming-more-common-134656">zoonotic pathway</a>.</p>
<p>While the likelihood of a pathogen emerging from melting ice and causing catastrophic extinctions is low, our results show this is no longer a fantasy for which we shouldn’t prepare.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/539709/original/file-20230727-25-ftjegw.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">They may only be microscopic – and far from the giant flesh-eating bugs you’ll see in sci-fi films – but the risks posed by pathogens shouldn’t be underestimated.</span>
<span class="attribution"><a class="source" href="https://cloud.blender.org/p/gallery/629f23f908e12d4ff15241d3">Giovanni Strona, 2023 (based on previous work by Oksana Dobrovolska)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/209795/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Corey J. A. Bradshaw receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Giovanni Strona does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Researchers simulated thousands of scenarios of an ancient pathogen being released into modern ecosystems. In the worst cases, up to one-third of host species were destroyed.Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Models Theme Leader for the ARC Centre of Excellence for Australian Biodiversity and Heritage, Flinders UniversityGiovanni Strona, Doctoral program supervisor, University of HelsinkiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2077852023-06-23T15:51:06Z2023-06-23T15:51:06ZThe melting Arctic is a crime scene. The microbes I study have long warned us of this catastrophe – but they are also driving it<p>The Arctic’s climate is warming at least four times faster than the global average, causing irrevocable changes to this vast <a href="https://news.sky.com/story/dramatic-changes-to-polar-ice-caps-revealed-on-new-map-of-arctic-and-antarctica-12898550">landscape</a> and precarious <a href="https://www.nwf.org/Educational-Resources/Wildlife-Guide/Wild-Places/Arctic#:%7E:text=The%20Arctic%20is%20a%20unique,in%20the%20summer%20to%20breed.">ecosystem</a> – from the anticipated <a href="https://earth.org/polar-bears-to-become-extinct-by-2100/">extinction of polar bears</a> to the <a href="https://www.scientificamerican.com/article/as-arctic-sea-ice-melts-killer-whales-are-moving-in/#:%7E:text=Killer%20whales%20often%20feed%20on,navigate%20through%20the%20icy%20waters.">appearance of killer whales</a> in ever-greater numbers. A new <a href="https://www.nature.com/articles/s41467-023-38511-8">study</a> suggests the Arctic Ocean could be ice-free in summer <a href="https://theconversation.com/arctic-ocean-could-be-ice-free-in-summer-by-2030s-say-scientists-this-would-have-global-damaging-and-dangerous-consequences-206974">as soon as the 2030s</a> – around a decade earlier than previously predicted.</p>
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<a href="https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Arctic sea ice changes" src="https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=700&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=700&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=700&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=879&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=879&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532508/original/file-20230618-17-lemk5e.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=879&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A new Arctic sea ice map compares the 30-year average with recent ten-year averages.</span>
<span class="attribution"><a class="source" href="https://www.bas.ac.uk/media-post/new-map-of-polar-regions-updated-to-reflect-ice-loss-name-changes-and-new-data/">British Antarctic Survey</a></span>
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<p>But to properly understand the pace and force of what’s to come, we should instead focus on organisms too small to be seen with the naked eye. These single-celled microbes are both the watchkeepers and arch-agitators of the Arctic’s demise.</p>
<p>Scientists like me who study them have become forensic pathologists, processing crime scenes in our Arctic field sites. We don the same white anti-contamination suits, photograph each sampling site, and bag our samples for DNA analysis. In some areas, red-coloured microbes even create an effect known as “blood snow”.</p>
<p>In this complex criminal investigation, however, the invisible witnesses are also responsible for the damage being done. Microbes testify to the vulnerability of their Arctic habitats to the changes that humans have caused. But they also create powerful climate feedback loops that are doing ever-more damage both to the Arctic, and the planet as a whole.</p>
<h2>Zipping headlong into icy oblivion</h2>
<p>My first visit to the Arctic was also nearly my last. As a PhD student in my early 20s in 2006, I had set out with colleagues to sample microbes growing on a glacier in the Norwegian archipelago of <a href="https://www.theguardian.com/environment/2023/may/13/svalbard-the-arctic-islands-where-we-can-see-the-future-of-global-heating">Svalbard</a> – the planet’s northernmost year-round settlement, about 760 miles from the North Pole.</p>
<p>Our treacherous commute took us high above the glacier, traversing an icy scree slope to approach its flank before crossing a river at the ice’s margin. It was a route we had navigated recently – yet this day I mis-stepped. Time slowed as I slid towards the stream swollen with ice melt, my axe bouncing uselessly off the glassy ice. I was zipping headlong into icy oblivion.</p>
<p>In that near-death calm, two things bothered me. The water would carry me deep into the glacier, so it would be decades before my remains were returned to my family. And the ear-worm of that field season meant I would die to the theme tune to Indiana Jones.</p>
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<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This article is part of Conversation Insights</em></strong>
<br><em>The Insights team generates <a href="https://theconversation.com/uk/topics/insights-series-71218">long-form journalism</a> derived from interdisciplinary research. The team is working with academics from different backgrounds who have been engaged in projects aimed at tackling societal and scientific challenges.</em></p>
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<p>Thankfully, the scree slowed my slide – I lived and learned, quickly, that dead scientists don’t get to write up their papers. And I’m still learning about the tiny organisms that populate every habitat there: from seawater in the Arctic Ocean to ice crystals buried deep in the <a href="https://en.wikipedia.org/wiki/Greenland_ice_sheet">Greenland ice sheet</a>.</p>
<p>These micro-managers of all manner of planetary processes are acutely sensitive to the temperatures of their habitats. The slightest change above freezing can transform an Arctic landscape from a frozen waste devoid of liquid water to one where microbes get busy reproducing in nutrient-rich water, transforming themselves in ways that <a href="https://www.nature.com/articles/ismej2010108">further amplify</a> the effects of climate warming.</p>
<p>The Svalbard region is now warming seven times faster than the global average. While much of the world continues its efforts to limit global warming to 1.5°C above pre-industrial levels, in the Arctic, that battle was lost long ago.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0VOGGdeB8eI?wmode=transparent&start=17" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Joseph Cook’s film on the microbes that inhabit the Greenland ice sheet.</span></figcaption>
</figure>
<h2>Decades ahead of us all</h2>
<p>It’s 2011, and <a href="http://www.earth.s.chiba-u.ac.jp/english/education/education02/staff16.html">Nozomu Takeuchi</a> is visiting Svalbard from Japan. It has been a difficult year back home, following the earthquake, tsunami and Fukushima nuclear incident, but Nozomu – a glacier ecologist and professor at Chiba University – is unrelenting in his quest to measure the effects of climate change. </p>
<p>Just hours after he stepped off a plane in the August midnight sun at Longyearbyen airport, we are marching up the nearest glacier. Above us, snow-capped mountain sides loom out of the swirling mist.</p>
<p>Since the 1990s, Nozomu has been collecting samples and measurements from glaciers all over the world. When we reach our goal near the snowline, he opens his rucksack to reveal a bento box full of sampling kit – stainless steel scoops, test tubes, sample bags, all arranged for efficiency. As he scurries around with practised efficiency, I think of offering help but fear I would only slow him down.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientist takes a reading in snowy Arctic landscape" src="https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532612/original/file-20230619-27-w8e0xr.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Nozomu Takeuchi measuring the biological darkening of a Svalbard glacier in 2011.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In truth, Nozomu is decades ahead of us all. Years ago, he made the link between the future of life and the death of ice, and these melting Svalbard glaciers are adding yet more points to his graphs.</p>
<p>Just as we apply oodles of factor 50 to protect ourselves from the Sun, so the billions of microbes sandwiched between the sky and surface of the glacier protect themselves by accumulating sunscreen-like pigments. And if enough of these pigments rest in one place under the Sun, this area of “biological darkening” absorbs the heat of the Sun much more effectively than reflective white snow and ice – so it melts faster.</p>
<p>Nozomu scoops up some of the so-called blood snow, heavily laden with algae. Under the microscope, their cells are indeed reminiscent of red blood cells. But rather than haemoglobin, these cells are laden with carotenoids – pigments also found in vegetables that <a href="https://academic.oup.com/femsec/article/94/3/fiy007/4810544?login=false">protect the algae from overheating</a>. Other patches of the glacier are verdant green, rich in algae that are busy photosynthesising light into chemical energy in this 24-hour daylight world.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man in icy landscape holding scientific sample" src="https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532611/original/file-20230619-29-l44kho.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The author with a sample of ‘blood snow’, collected from a glacier surface.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Further down the glacier, the professor crushes some “dirty” ice into a bag. A different kind of algae lives here that, depending on your point-of-view, is either black, brown or purple (perhaps it depends on the tint of your sunglasses). The <a href="https://www.researchgate.net/figure/Chemical-structure-of-compound-3-purpurogallin-carboxylic-acid-6-O-b-d-glucopyranoside_fig2_51806131#:%7E:text=A%20gallotannin%20derivative%20(galloylglucopyranose%2C%20i.e.,et%20al.%2C%202012b)%20.">pigment</a> created is like the compounds that colour tea, and the algae keep it in layers like parasols above the photosynthetic factories within their cells – ensuring they have just enough sunlight to photosynthesise, but not enough to burn.</p>
<p>Open Google Earth and as you zoom in on the Arctic, you may spot the large dark stripe that scars the western margin of the <a href="https://en.wikipedia.org/wiki/Greenland_ice_sheet">Greenland ice sheet</a>. This is the “dark zone”, but it’s not caused by dark <a href="https://www.nature.com/articles/s41467-020-20627-w">dust</a> or soot. It’s alive, <a href="https://www.nature.com/articles/ismej2012107">laden with algae</a> – and it has been darkening, and growing, as Greenland warms.</p>
<p>Between 2000 and 2014, the <a href="https://www.frontiersin.org/articles/10.3389/feart.2016.00043/full">dark zone’s area grew by 14%</a>. At 279,075 km² in 2012, it was already more than twice the <a href="https://www.britannica.com/summary/England#:%7E:text=Area%3A%2050%2C301%20sq%20mi%20(130%2C278,even%20with%20the%20entire%20kingdom.).%20This%20had%20a%20powerful%20impact%20on%20the%20rate%20of%20ice%20melt%20--%20areas%20blooming%20with%20algae%20%5Bmelt%20nearly%202cm%20more%20each%20day%5D(https://www.pnas.org/doi/abs/10.1073/pnas.1918412117">size of England</a> than bare ice.</p>
<p>Next morning, I am woken by the smell of chemicals, having slept beneath a coffee table. Nozomu is busy processing his samples: bags of melting ice pinned to a clothesline by bulldog clips. They resemble bunting around the crowded room, but this is no time for celebration. The tint of each bag adds a measurement which quantifies the link between these algae, their pigments, and the death of their icy home.</p>
<h2>The case becomes urgent</h2>
<p>By the summer of 2014, glaciologists all over the world have started to listen to the warnings of pioneering ecologists such as Nozomu. The glaciers are dying even as life blossoms on their darkening surfaces. The case has become urgent.</p>
<p>I am in a helicopter, flying with colleagues to a camp in the dark zone on the Greenland ice sheet – the largest mass of glacial ice in the northern hemisphere. Covering 1.7 million km², its ice holds the equivalent of the water required to raise global sea levels by 7.7 metres.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A landscape of dark ice intertwined with blue rivers of meltwater." src="https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532620/original/file-20230619-23-shc4a3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A highly darkened surface of the Greenland ice sheet, rich in algae and incised with rivers of meltwater.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>As we warm our climate, the rate of water flowing from this reservoir increases, with each degree Celsius added to global temperatures opening the drainage valve even wider. Feedback processes such as biological darkening have the potential to multiply the number of drainage valves that are open, hastening dramatically the rate at which sea levels rise.</p>
<p>To monitor this effect, every day <a href="https://www.gla.ac.uk/schools/ges/staff/karencameron/">Karen Cameron</a>, the leader of our camp this summer, walks to undisturbed patches of ice carrying a £100,000 backpack which contains a spectrometer to measure the darkness of the ice, capturing how it absorbs the solar energy that causes melting. The glaciologists are desperate for ground truth, and their models need data.</p>
<p>Up to this point, none of their predictions of how the Greenland ice sheet would respond to our warming climate have included biological darkening. Even if the effect were modest, it could still topple the ice sheet from a predictable, straightline response to climate warming.</p>
<p>All the time we are in Greenland, the only lifeforms we encounter are the flies that hatch from the fresh fruit and peppers in our food rations. These and the few types of glacier algae and several hundred kinds of bacteria that are biologically darkening the ice: a living scum scarring the surface of the ice sheet.</p>
<p>My work focuses on how these tiny organisms adapt to their icy habitat, but the implications of their behaviour are now of global concern. A <a href="https://screenworks.org.uk/archive/baftss-practice-research-award-2017/timeline">filmmaker</a> at the camp is weaving a thread between the ice melt in Greenland and its consequences for people living in coastal communities all over the world – from villages near my home on the <a href="https://www.theguardian.com/environment/2019/may/18/this-is-a-wake-up-call-the-villagers-who-could-be-britains-first-climate-refugees">west coast of Wales</a>, to huge metropolises like Manhattan, Amsterdam and Mumbai, and even entire low-lying island nations in the Pacific.</p>
<p>As smaller glaciers fade, and the larger ice sheets of Greenland and Antarctica start to respond with full force to our warming climate, it is these communities, capitals and countries that will bear the brunt of the flooding, inundation and erosion that comes with rising sea levels.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two scientists inspecting an ice corer device dripping with meltwater." src="https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532622/original/file-20230619-28-oh4l8z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The author (left) and Joseph Cook high on the Greenland ice sheet, meltwater dripping from their ice corer.</span>
<span class="attribution"><span class="source">Sara Penrhyn Jones</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Before heading home, our helicopter takes us on a detour, high over the ice sheet. We fly over the brown-black-purple algae to brighter, higher elevations where the palette shrinks to the blue and white of water and ice, then snow and sky. Greenland makes its own weather and, in these higher elevations, we expect the ice to be frozen all year round. When we land and begin to collect snow samples and a small ice core, however, we find we are digging into slush. The ice has started to melt up here, too. </p>
<p>We heave up our ice corer, and meltwater dribbles out from its bottom. In periods of extreme warming, much of the surface of the ice sheet can experience melting episodes, <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2015.00225/full">disturbing the slumbering microbes</a> stored within the otherwise permanently frozen surface. It’s a sobering moment for us all.</p>
<p>Flying back to camp, I watch the streams become rivers and lakes as we head back over the dark zone, where melt and microbes dominate the icescape. I contemplate how much water, once locked in the ice, will become free to flow into the sea and into millions of homes by the end of the century.</p>
<h2>Popping a pingo</h2>
<p>The frozen lands of eight nations encircle the Arctic. Their soils store vast quantities of carbon: a third of the planet’s entire quantity of soil carbon resides in this frozen ground.</p>
<p>The carbon is a legacy of soils formed in past climates and preserved for millennia. However, human-induced climate change is reheating this leftover carbon, providing a luxuriant food source for microbes resident within the <a href="https://earthobservatory.nasa.gov/biome/biotundra.php">tundra</a>, which then emit it as greenhouse gases.</p>
<p>This is known as the <a href="https://en.wikipedia.org/wiki/Permafrost_carbon_cycle#:%7E:text=Carbon%20emissions%20from%20permafrost%20thaw,which%20increases%20permafrost%20thaw%20depths.">permafrost carbon</a> feedback loop. When even modest quantities of this vast carbon store reach the atmosphere, warming accelerates – resulting in faster thawing of the tundra and the release of yet more greenhouse gases.</p>
<p>Furthermore, not all greenhouse gases are equal in their impact. While carbon dioxide is relatively abundant and stable for centuries in the atmosphere, methane is less abundant and shorter-lived, but remarkably powerful as a greenhouse gas – nearly 30 times more damaging to the climate than carbon dioxide, for the same volume.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientist crouched on ice taking water samples." src="https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=307&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=307&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=307&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=386&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=386&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532615/original/file-20230619-1823-ekek0j.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=386&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Andy Hodson sampling methane from a freshly ‘popped’ pingo.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>For more than three decades, <a href="https://www.unis.no/staff/andy-hodson/">Andy Hodson</a> has worked at the frontier where microbes, carbon and the Arctic landscape meet. In 2018, we join him on a brisk spring day in Svalbard. It’s -26°C but the snowmobile commute is thankfully brief – then we work quickly against the cold.</p>
<p>Hodson’s plan is to “pop” one of the many <a href="https://en.wikipedia.org/wiki/Pingo">pingos</a> that populate the floor of this wide open valley. Think of pingos as the acne of the Arctic: they form as permafrost compresses unfrozen wet sediments, erupting as small hills blistering the skin of the tundra.</p>
<p>The story of these microbes’ lives is complicated. They only live beyond the reach of oxygen – where oxygen is more prevalent, methane-consuming microbes thrive instead, quenching the belches of methane from below. Similarly, should mineral sources of iron or sulphide be nearby, then microbes that use them outcompete the methanogens.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small fountain of water in an opening in the ice, amid a snowy landscape." src="https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532614/original/file-20230619-15-6i78fv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A popped pingo discharging supercooled water rich in methane.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It all adds up to one of the greatest uncertainties for our civilisation: the extent and composition of greenhouse gases escaping from Arctic lands. <a href="https://www.cam.ac.uk/research/news/emissions-from-melting-permafrost-could-cost-43-trillion#:%7E:text=Increased%20greenhouse%20gas%20emissions%20from,and%20the%20University%20of%20Colorado.">Estimates of the economic impacts</a> from this permafrost carbon feedback tally in the tens of trillions of dollars to the global economy. We know it is bad news, but exactly how bad depends on the microbes in their microscopic mosaic.</p>
<p>Hodson’s field work shows that, during the Arctic winter, this pingo is probably the only source of methane in the immediate area, its chimney enabling the gas to escape from the depths of the ice before methane-consuming microbes can catch it. Annually, tens of kilograms of methane and more than a ton of carbon dioxide will escape from this pingo alone - one of <a href="https://doi.org/10.1016/j.geomorph.2023.108694">more than 10,000</a> scattered across the Arctic, in addition to its other methane-producing hotspots.</p>
<h2>A near-perfect ecosystem</h2>
<p>Arctic lands are a patchwork of permafrost carbon feedbacks, and our future depends on the uncertain fate of the microbes within. </p>
<p>While the ice melt enhances the growth of microbes in the short term, if it continues to the point of erasing habitats then the microbes will be lost with them. We recognise this danger for polar bears and walruses, but not the invisible biodiversity of the Arctic. Small does not mean insignificant though.</p>
<p>To appreciate this, we can head back to the dark zone on Greenland’s ice sheet and join <a href="https://www.rolex.org/rolex-awards/exploration/joseph-cook">Joseph Cook</a> during our summer 2014 field season. He’s lying on a mat improvised from a bath towel and a binbag wrapped in duct tape, peering into a dark, pothole-like depression in the ice. It’s a cryoconite hole, and millions of them are dotted over the edges of the ice sheet. Where pingos contribute to climate warming by emitting methane, cryoconite is a good sink of greenhouse gases, but this creates its own problems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Crouching scientist takes samples in the Arctic snow." src="https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532618/original/file-20230619-27-4a5amn.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Joseph Cook measuring the carbon cycling activities of Greenland’s cryoconite holes.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01758.x">earliest estimate</a> of its ability to store carbon dioxide from the air on the ice surface of the world’s glaciers exceeded Finland’s total carbon emissions in the same year. Every cryoconite hole is a near-perfect ecosystem – with a singular flaw. Its inhabitants must melt ice to live. But the very act of melting the ice hastens the demise of their glacier habitat. </p>
<p>Despite being found in some of the harshest locations on Earth, cryoconite is home for thousands of different types of bacteria (including the all-important photosynthetic cyanobacteria), fungi, and <a href="https://microbiologysociety.org/why-microbiology-matters/what-is-microbiology/protozoa.html">protozoa</a>. Even <a href="https://www.theguardian.com/environment/2020/oct/17/tardigrade-ice-hole-arctic-greenland">tardigrades</a> thrive in cryoconite.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Microscope image of a single cryoconite granule." src="https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532623/original/file-20230619-21-7v4otj.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microscope image of a cryoconite granule, showing biological darkening and cyanobacteria growing through it.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Cook is professionally besotted with the perfection of this near-frozen “microscopic rainforest”. Its inhabitants are shielded and nourished at just the right depth and in the right shape for a busy ecosystem to be engineered by the interaction of sunlight with cyanobacteria, dust and ice to the benefit of all its inhabitants. The cyanobacteria use sunshine to capture carbon dioxide from the air and convert it into the slimy cement that builds each granule of cryoconite</p>
<p>However, with vast numbers of cryoconite holes dotted across the ice surface, “swarms” of these holes help <a href="https://www.frontiersin.org/articles/10.3389/feart.2015.00078/full">shape and darken the ice surface</a>. This in turn influences the melting rate, as the surface is sculpted under the sun of 24-hour daylight.</p>
<p>Writing in the scientific journal <a href="https://www.nature.com/articles/029039a0">Nature in 1883</a>, Swedish polar explorer Adolf Erik Nordenskjöld, who discovered cryoconite, thanked the organisms within cryoconite for melting away the ancient ice that once covered Norway and Sweden:</p>
<blockquote>
<p>In spite of their insignificance, [they] play a very important part in nature’s economy, from the fact that their dark colour far more readily absorbs the Sun’s heat than the bluish-white ice, and thereby they contribute to the destruction of the ice sheet, and prevent its extension. Undoubtedly we have, in no small degree, to thank these organisms for the melting away of the layer of ice which once covered the Scandinavian peninsula.</p>
</blockquote>
<h2>Taking DNA analysis to strange new places</h2>
<p>We return to Greenland in winter 2018 to explore cryoconite’s singular flaw. Cook and I are joined by Melanie Hay, then a PhD student in Arctic bioinformatics.</p>
<p>Hay and I are taking DNA analysis to strange new places to learn more about the evolution and biology of cryoconite. Powerful advances in genomics are changing our view of the microbial world, but large DNA-sequencing instruments fare best in sophisticated labs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientist sitting outside her tent with backpack, looking out at icy landscape." src="https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532619/original/file-20230619-17-uv14gu.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Melanie Hay camping and sampling on the Greenland ice sheet.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Instead, we are using a stapler-sized nanopore sequencer hooked up to the USB port of a winterised laptop. Outside the tent, it is –20°C – but the DNA sequencer must run at body temperature. The only sustainable source of warmth is body heat, so I have snuggled up with the sequencer in my sleeping bag every night and in my clothes all day.</p>
<p>That evening, we are caught in a storm of hurricane force. Becoming disorientated while moving between tents would be lethal, so we crawl in a human chain through the whiteout to our sleeping tents. Hay reaches her tent but Cook’s is lost, so we squeeze into my one-person tent. Somehow I sleep soundly, while Cook is exposed to the full force of the night’s terror.</p>
<p>In the morning, we excavate Hay, whose snow-laden tent had collapsed in the night. The sequencing is complete, but storm damage to our generator means the camp is losing power, so she must work quickly. She identifies the cyanobacteria building the cryoconite – it’s a short list dominated by one species: <em>Phormidesmis priestleyi</em>.</p>
<p>This species, found in cryoconite throughout the Arctic, seems to be the ecosystem engineer of cryoconite – a microscopic beaver building a dam of dust. But the flaw is the darkness of the near-perfect cryoconite ecosystems it creates. Like the neighbouring glacier algae we met earlier, <em>Phormidesmis priestleyi</em> is biologically darkening Arctic ice, and eventually hastening the demise of the thousands of different types of organism contained in cryoconite holes.</p>
<p>And so, this work shows us ever more clearly that the <a href="https://www.nature.com/articles/s41559-020-1163-0">loss of the planet’s glaciers</a> is as much a component of the global biodiversity crisis as it is a headline impact of climate change.</p>
<h2>Last line of defence against antibiotic resistance</h2>
<p>The loss of the Arctic’s microbial biodiversity matters in other ways too. Hay and Aliyah Debbonaire are both reformed biomedical scientists seeking cures from the Arctic in the form of new antibiotics. In the summer of 2018, we are in Svalbard looking for clues.</p>
<p>The world is running out of effective antibiotics, and the Arctic’s frontiers may be our last line of defence in this antibiotic resistance crisis. Countless species of microbes have evolved to live within its harsh habitats using all the tricks in the book, including making antibiotics as chemical weapons to kill off competitors. This means they may be sources of new antibiotics.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scientists (one kneeling) taking samples in the snowy Arctic landscape." src="https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532631/original/file-20230619-1900-kr9gwx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aliyah Debbonaire (left) and Melanie Hay sampling a cryoconite hole.</span>
<span class="attribution"><span class="source">Arwyn Edwards</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>And this is not their only application. From cheeses to eco-friendly biological washing powders, entire shopping aisles of products have been derived from cold-adapted microbes. As climate warming threatens to disrupt entire Arctic habitats, our opportunity to use, learn from, and protect this biodiversity may be lost forever.</p>
<p>As our tiny plane returns to the nearest town, Longyearbyen, we fly low over the <a href="https://theconversation.com/after-svalbard-why-safety-of-world-seed-vaults-is-crucial-to-future-food-security-79586">Svalbard Global Seed Vault</a>, which contains the fruits of more than 12,000 years of agriculture in the form of seeds from a million different varieties of crop. Nearby, a similar facility inside a disused coal mine stores essential computer programmes on microfilm – the ultimate backup for our data-addicted world.</p>
<p>Within a snowy kilometre, you can walk between the the alpha and omega of human innovation in civilisation. Both facilities have chosen the fastest-warming town on the planet as the safest place to store these treasures of humanity. Yet no such facility is dedicated to the microbial biodiversity of the Arctic, despite its critical importance to the future of the world’s biotech and medical sectors.</p>
<p>Instead, it falls to microbiologists such as Debbonaire, racing against time to identify, nurture and screen the microbes of the melting Arctic. Her painstaking work accumulates towers of Petri dishes, each a temporary refuge for a different Arctic microbe.</p>
<p>Eventually, they will be stored in <a href="https://www.dellamarca.it/en/how-does-an-ultra-low-freezer-work/">ultra-freezers</a> in laboratories scattered across the world. Such work is unglamorous to funders, so it is done piecemeal on the edges of other projects. Yet it represents our only attempt to save the microbes of the Arctic.</p>
<h2>The battle is lost</h2>
<p>Most of all, the Arctic matters because it is the fastest-warming part of the planet, and its microbes are responding first. What happens there carries implications for everyone. It is the harbinger of change for everywhere.</p>
<p>Another Arctic microbiologist could strike plangent notes regarding permafrost or sea ice, but as an ecologist of glaciers I am drawn to glacial ice.</p>
<p>Over the first fifth of this century, Earth’s glaciers have discharged some ten quadrillion (ten to the power 25) tablespoons of melt a year – and within each tablespoon, the <a href="https://www.nature.com/articles/s43247-022-00609-0">tens of thousands of bacteria and viruses</a> that were once stored within that ice.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/meltwater-is-infiltrating-greenlands-ice-sheet-through-millions-of-hairline-cracks-destabilizing-its-structure-207468">Meltwater is infiltrating Greenland’s ice sheet through millions of hairline cracks – destabilizing its structure</a>
</strong>
</em>
</p>
<hr>
<p>What’s to come is sadly predictable. Even the most modest warming scenario of 1.5°C above the pre-industrial era will lead to the extinction of at least <a href="https://www.science.org/doi/10.1126/science.abo1324">half the Earth’s 200,000 glaciers</a> by the end of the century.</p>
<p>Depending on the urgency and effectiveness of our actions as a civilisation, this century could also represent the “peak melt” in our history. Yet the battle to save many of these precious icy habitats is already lost. Instead, for scientists like me, our field work is now largely a question of documenting these “crime scenes” – so at least the knowledge of life within ice can be preserved, before it melts away forever.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=112&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=112&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=112&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=140&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=140&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=140&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
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<p class="fine-print"><em><span>Arwyn Edwards receives funding from UK Research & Innovation - Natural Environment Research Council, as well as the Research Council of Norway, the Leverhulme Trust, and the Royal Geographical Society. </span></em></p>To fully understand the extent of climate-related dangers the Arctic – and our planet – is facing, we must focus on organisms too small to be seen with the naked eye.Arwyn Edwards, Reader in Biology, Department of Life Sciences, Aberystwyth UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2032772023-04-06T11:24:18Z2023-04-06T11:24:18ZNew research shows how rapidly ice sheets can retreat – and what it could mean for Antarctic melting<figure><img src="https://images.theconversation.com/files/519798/original/file-20230406-20-zctnfl.jpg?ixlib=rb-1.1.0&rect=38%2C6%2C4272%2C2833&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A glacier in Paradise Bay, Antarctica.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/glacier-paradise-bay-antarctica-2227007003">jet 67/Shutterstock</a></span></figcaption></figure><p>The <a href="https://www.bas.ac.uk/about/antarctica/geography/ice/">Antarctic Ice Sheet</a>, which covers an area greater than the US and Mexico combined, holds enough water to raise global sea level by <a href="https://www.nature.com/articles/s41561-019-0510-8">more than 57 metres if melted completely</a>. This would flood hundreds of cities worldwide. And evidence suggests it is melting fast. Satellite observations have revealed that grounded ice (ice that is in contact with the bed beneath it) in coastal areas of West Antarctica has been lost at a rate of <a href="https://www.nature.com/articles/s41561-021-00877-z">up to 30 metres per day</a> in recent years. </p>
<p>But the satellite record of ice sheet change is relatively short as there are only 50 years’ worth of observations. This limits our understanding of how ice sheets have evolved over longer periods of time, including the maximum speed at which they can retreat and the parts that are most vulnerable to melting. </p>
<p>So, we set out to investigate how ice sheets responded during a previous period of climatic warming – the last “deglaciation”. This climate shift occurred between roughly 20,000 and 11,000 years ago and spanned Earth’s transition from a glacial period, when ice sheets covered large parts of Europe and North America, to the period in which we currently live (called the <a href="https://www.ncei.noaa.gov/sites/default/files/2021-11/12%20Mid-Holocene%20Warm%20Period%20%26%20Penultimate%20Interglacial%20Period%20%26%20Early%20Eocene%20Period%20-FINAL%20OCT%202021.pdf">Holocene interglacial period</a>). </p>
<p>During the last deglaciation, rates of temperature and sea-level rise were broadly comparable to today. So, studying the changes to ice sheets in this period has allowed us to estimate how Earth’s two remaining ice sheets (Greenland and Antarctica) might respond to an even warmer climate in the future.</p>
<p>Our <a href="https://www.nature.com/articles/s41586-023-05876-1">recently published results</a> show that ice sheets are capable of retreating in bursts of up to 600 metres per day. This is much faster than has been observed so far from space.</p>
<figure class="align-center ">
<img alt="A satellite image showing blocks of ice floating in the ocean." src="https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/519800/original/file-20230406-26-vgkg3h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Satellite imagery reveals that Earth’s ice sheets are retreating fast.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/glacier-greenland-blocks-ice-floating-ocean-1750617149">Trismegist san/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Pulses of rapid retreat</h2>
<p>Our research used <a href="https://mareano.no/en">high-resolution maps</a> of the Norwegian seafloor to identify small landforms called “corrugation ridges”. These 1–2 metre high ridges were produced when a former ice sheet retreated during the last deglaciation. </p>
<p>Tides lifted the ice sheet <a href="https://www.science.org/doi/10.1126/science.aaz3059">up and down</a>. At low tide, the ice sheet rested on the seafloor, which pushed the sediment at the edge of the ice sheet upwards into ridges. Given that there are two low tides each day off Norway, two separate ridges were produced daily. Measuring the space between these ridges enabled us to calculate the pace of the ice sheet’s retreat. </p>
<p>During the last deglaciation, the <a href="https://www.britannica.com/place/Scandinavian-Ice-Sheet">Scandinavian Ice Sheet</a> that we studied underwent pulses of extremely rapid retreat – at rates between 50 and 600 metres per day. These rates are up to 20 times faster than the highest rate of ice sheet retreat that has so far been measured in Antarctica from satellites. </p>
<p>The highest rates of ice sheet retreat occurred across the flattest areas of the ice sheet’s bed. In flat-bedded areas, only a relatively small amount of melting, of around half a metre per day, is required to instigate a pulse of rapid retreat. Ice sheets in these regions are very lightly attached to their beds and therefore require only minimal amounts of melting to become fully buoyant, which can result in almost instantaneous retreat.</p>
<p>However, rapid “buoyancy-driven” retreat such as this is probably only sustained over short periods of time – from days to months – before a change in the ice sheet bed or ice surface slope farther inland puts the brakes on retreat. This demonstrates how nonlinear, or “pulsed”, the nature of ice sheet retreat was in the past. </p>
<p>This will likely also be the case in the future.</p>
<h2>A warning from the past</h2>
<p>Our findings reveal how quickly ice sheets are capable of retreating during periods of climate warming. We suggest that pulses of very rapid retreat, from tens to hundreds of metres per day, could take place across flat-bedded parts of the Antarctic Ice Sheet even under <a href="https://tc.copernicus.org/articles/13/2633/2019/">current rates of melting</a>. </p>
<p>This has implications for the vast and potentially unstable <a href="https://thwaitesglacier.org/about/facts">Thwaites Glacier</a> of West Antarctica. Since scientists began observing ice sheet changes via satellites, Thwaites Glacier has experienced <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014GL060140">considerable retreat</a> and is now only 4km away from a flat area of its bed. Thwaites Glacier could therefore suffer pulses of rapid retreat in the near future.</p>
<p>Ice losses resulting from retreat across this flat region could accelerate the rate at which ice in the rest of the Thwaites drainage basin collapses into the ocean. The Thwaites drainage basin contains enough ice to <a href="https://thwaitesglacier.org/about/facts">raise global sea levels by approximately 65cm</a>.</p>
<figure class="align-center ">
<img alt="The Fimbul Ice Shelf in East Antarctica." src="https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/519513/original/file-20230405-26-wcune3.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Fimbul Ice Shelf in East Antarctica.</span>
<span class="attribution"><span class="source">Christine Batchelor</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our results shed new light on how ice sheets interact with their beds over different timescales. <a href="https://www.sciencedirect.com/science/article/pii/S092181811630491X">High rates of retreat</a> can occur over decades to centuries where the bed of an ice sheet deepens inland. But we found that ice sheets on flat regions are most vulnerable to extremely rapid retreat over much shorter timescales. </p>
<p>Together with data about the shape of ice sheet beds, incorporating this short-term mechanism of retreat into computer simulations will be critical for accurately predicting rates of ice sheet change and sea-level rise in the future.</p><img src="https://counter.theconversation.com/content/203277/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frazer Christie receives funding from the Prince Albert II of Monaco Foundation. </span></em></p><p class="fine-print"><em><span>Christine Batchelor does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Seafloor landforms reveal that ice sheets can collapse at 600 metres per day.Christine Batchelor, Lecturer in Physical Geography, Newcastle UniversityFrazer Christie, Postdoctoral Research Associate, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2006222023-03-16T19:57:32Z2023-03-16T19:57:32ZThe Rideau Canal Skateway: How can we promote resilience in the face of a changing climate?<figure><img src="https://images.theconversation.com/files/515295/original/file-20230314-1765-t25qdd.jpg?ixlib=rb-1.1.0&rect=279%2C203%2C5363%2C3553&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Even if we achieve our global commitment to limit temperature increase to less than 2 C this century, climate change will continue to impact the culturally significant Rideau Canal Skateway.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p><a href="https://ncc-ccn.gc.ca/places/history-rideau-canal-skateway">Rideau Canal Skateway</a>, the 7.8 kilometre ice path winding through the Canadian capital city of Ottawa, is a <a href="https://www.pc.gc.ca/culture/spm-whs/sites-canada/sec02n">National Historic Site of Canada</a> and a <a href="https://whc.unesco.org/en/list/1221">UNESCO World Heritage Site</a>. </p>
<p>This winter, for the first time, the Rideau Canal Skateway <a href="https://ncc-ccn.gc.ca/news/ncc-efforts-to-open-the-rideau-canal-skateway-come-to-an-end">did not open</a>.</p>
<p>Although transforming the Rideau Canal waterway into the winter skateway — which typically welcomes more than 21,000 visitors on average per day — requires considerable <a href="https://ncc-ccn.gc.ca/blog/rideau-canal-behind-the-ice">engineering and logistical effort</a>, the ice cover growth is ultimately governed by the ambient environmental conditions.</p>
<p>Even if we achieve our <a href="https://www.un.org/en/climatechange/paris-agreement">global commitment to limit temperature increase to less than 2 C this century</a>, climate change will continue to impact this culturally significant Canadian heritage site. <a href="https://www.ipcc.ch/ar6-syr/">Global warming is known to impact</a> our ecosystems, biodiversity, food security and infrastructure. </p>
<p>Recent studies have observed decreases in the <a href="https://doi.org/10.1002/hyp.8068">seasonal duration</a> and area coverage of <a href="https://doi.org/10.1038/s41558-018-0393-5">lake and river ice</a>, with long-term negative impacts projected for <a href="https://doi.org/10.1038/nclimate2465">recreational facilities</a>.</p>
<p>And while the National Capital Commission (NCC) has been working towards advancing sustainable adaptation strategies that promote the resilience of such climate change-impacted areas, it needs to be supported with informed decision-making. Our research at Carleton University, in collaboration with the NCC, will establish an adaptive framework to support this strategy.</p>
<h2>Effects of the changing climate</h2>
<p>Since 1971, the average Rideau Canal Skateway season lasted 57 days. Over the past five seasons (2017-22) the average season length dropped down to 47 days. The longest season of 90 days took place in the winter of 1971-72, while the shortest season lasted 29 days in 2021-22. However, last winter, the full 7.8 kilometre stretch of the Skateway was accessible on opening day (Jan. 14, 2022) for the first time in over two decades.</p>
<p>This winter, the Rideau Canal Skateway <a href="https://ottawa.ctvnews.ca/rideau-canal-skateway-won-t-open-for-1st-time-in-53-year-history-1.6287966">never opened</a>. This can be attributed to warmer temperatures and twice the typical snowfall when compared with the climate normal from <a href="https://climate.weather.gc.ca/climate_normals/index_e.html">1981-2010</a>. </p>
<p>Meanwhile, Ottawa-Gatineau’s Winterlude festival was delayed by one day due to <a href="https://www.pressreader.com/canada/ottawa-sun/20230205/281505050370569">extreme cold conditions</a> with a mean temperature of -26 C and average windchill of -34 C on Feb. 4, 2023. This was despite the region experiencing warmer than normal temperatures in 2022-23.</p>
<p>These erratic weather patterns, occurring due to climate change, may become a more significant factor affecting the season start and ice-building processes in the future.</p>
<h2>Sustainable development strategy</h2>
<p>The National Capital Commission, in collaboration with local municipalities and government agencies, established a <a href="https://ncc-ccn.gc.ca/our-plans/climate-change-adaptation#doc1">sustainable development strategy</a> to evaluate the risk of climate change effects on infrastructure and heritage buildings, natural resources and parks. </p>
<p>This adaptation strategy has three phases: 1) climate projections, 2) vulnerability and risk assessment and 3) adaptation strategy.</p>
<figure class="align-center ">
<img alt="Winter in Ottawa." src="https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515301/original/file-20230314-6289-ldh9c8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In a high emission scenario, winters in the Ottawa region have been estimated to be five weeks shorter by 2050.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>One of the key findings of the first phase is that, in a high emission scenario, winters in the Ottawa region would be five weeks shorter by 2050 with 35 per cent fewer days below -10 C. The climate projections also estimated a decrease in annual snowfall by 20 per cent with an increase in freezing rain.</p>
<p>An outcome from the second phase was to address the climate hazards impacting infrastructure, heritage buildings, natural resources and parks, like the Rideau Canal Skateway, and advance possible adaptation strategies.</p>
<h2>Multi-disciplinary approach</h2>
<p>The <a href="https://ncc-ccn.gc.ca/blog/tackling-climate-change-on-the-rideau-canal-skateway">National Capital Commission</a> teamed up with <a href="https://newsroom.carleton.ca/story/rideau-canal-skating-changing-climate/">Carleton University</a> to develop an improved understanding of the climate-related hazards and find potential adaptation strategies to mitigate the effect of climate change and make the Rideau Canal Skateway more resilient.</p>
<p>The <a href="https://carleton.ca/geirg/about/climate-change-effects-rideau-canal-skateway/">multidisciplinary team</a> at Carleton has integrated researchers across the fields of physical geography, cryospheric science, civil and mechanical engineering and remote sensing. In collaboration with the NCC, we have begun a four-year research project with this goal in mind.</p>
<p>This project aims to:</p>
<p>1) improve our knowledge base on the physical environment of the Rideau Canal Skateway</p>
<p>2) use this data to simulate the effects of climate change projected forward over the next 10, 20 and 30 year periods</p>
<p>3) assess what makes the Skateway vulnerable to the effects of climate change</p>
<p>4) conduct pilot studies to evaluate possible adaptation strategies</p>
<p>5) refine and optimize the promising adaptation strategies that can help address the uncertain evolution of climate change in the future</p>
<p>We will explore what promotes ice growth at the beginning of the season when the environmental conditions are more favourable and the ice cover is too thin for supporting conventional equipment and techniques. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1601284163113742336"}"></div></p>
<p>The initial pilot studies will focus on the use of <a href="https://www.wsj.com/articles/ski-resorts-are-spending-big-on-snow-making-to-keep-ahead-of-climate-change-44e0931f">snow fans</a> or slush canons to promote ice growth (ice catching), reduced scale autonomous snow blowers (snow management) and heat exchangers, such as thermosyphons, that help cool the water below the ice (thermal management). </p>
<p>A dynamic pathway based on these studies will help the National Capital Commission to implement effective and sustainable adaptation strategies that maintain or improve the current levels of service for the next 30-year window.</p>
<h2>Broader view with global action</h2>
<p>The iconic significance of the Rideau Canal Skateway makes it an integral part of Ottawa’s cultural identity and our project aims to find climate change adaptation strategies to keep this intact.</p>
<p>Underpinning this research is the overarching need for a concerted <a href="https://www.un.org/en/climatechange">global community</a> response to the <a href="https://www.canada.ca/en/services/environment/weather/climatechange/climate-plan/national-adaptation-strategy.html">challenges of climate change</a>. </p>
<p>Such challenges also present <a href="https://www.forbes.com/sites/forbesfinancecouncil/2022/02/11/the-climate-fight-presents-massive-opportunity-for-businesses-investors/?sh=346331124055">opportunities</a> like economic growth and technology development in the energy transition market, which in turn has other benefits ranging from improved public health to job creation. Leveraging these benefits of <a href="https://www.ucsusa.org/resources/top-10-benefits-climate-action">climate action</a> can become the cornerstone of our climate change adaptation strategies.</p><img src="https://counter.theconversation.com/content/200622/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>As part of the NSERC Alliance grant, which leveraged funding from the National Capital Commisssion, the Principal Investigator Shawn Kenny consults with the National Capital Commission on the project outcomes to facilitate knowledge transfer and translation. </span></em></p>Erratic weather patterns occurring due to climate change may become a more significant factor affecting the season start and ice-building processes in the future.Shawn Kenny, Associate Professor, Department of Civil and Environmental Engineering, Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1881472022-08-05T04:10:26Z2022-08-05T04:10:26ZThe length of Earth’s days has been mysteriously increasing, and scientists don’t know why<figure><img src="https://images.theconversation.com/files/477777/original/file-20220805-17816-qkr00w.jpeg?ixlib=rb-1.1.0&rect=33%2C53%2C4459%2C2701&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Atomic clocks, combined with precise astronomical measurements, have revealed that the length of a day is suddenly getting longer, and scientists don’t know why.</p>
<p>This has critical impacts not just on our timekeeping, but also things like GPS and other technologies that govern our modern life.</p>
<p>Over the past few decades, Earth’s rotation around its axis – which determines how long a day is – has been speeding up. This trend has been making our days shorter; in fact, in June 2022 <a href="https://www.timeanddate.com/news/astronomy/shortest-day-2022">we set a record</a> for the shortest day over the past half a century or so. </p>
<p>But despite this record, since 2020 that steady speedup has curiously switched to a slowdown – days are getting longer again, and the reason is so far a mystery.</p>
<p>While the clocks in our phones indicate there are exactly 24 hours in a day, the actual time it takes for Earth to complete a single rotation varies ever so slightly. These changes occur over periods of millions of years to almost instantly – even earthquakes and storm events can play a role.</p>
<p>It turns out a day is very rarely exactly the magic number of 86,400 seconds. </p>
<h2>The ever-changing planet</h2>
<p>Over millions of years, Earth’s rotation has been slowing down due to friction effects associated with the tides driven by the Moon. That process adds about about 2.3 milliseconds to the length of each day every century. A few billion years ago an Earth day was only about <a href="https://www.science.org/content/article/average-earth-day-used-be-less-19-hours-long#:%7E:text=In%20timely%20news%2C%20scientists%20have,24%20hours%2C%20The%20Guardian%20reports">19 hours</a>.</p>
<p>For the past 20,000 years, another process has been working in the opposite direction, speeding up Earth’s rotation. When the last ice age ended, melting polar ice sheets reduced surface pressure, and Earth’s mantle started steadily moving toward the poles.</p>
<p>Just as a ballet dancer spins faster as they bring their arms toward their body – the axis around which they spin – so our planet’s spin rate increases when this mass of mantle moves closer to Earth’s axis. And this process shortens each day by about 0.6 milliseconds each century.</p>
<p>Over decades and longer, the connection between Earth’s interior and surface comes into play too. Major earthquakes can change the length of day, although normally by small amounts. For example, the Great Tōhoku Earthquake of 2011 in Japan, with a magnitude of 8.9, is believed to have sped up Earth’s rotation by a relatively tiny <a href="https://www.space.com/11115-japan-earthquake-shortened-earth-days.html">1.8 microseconds</a>. </p>
<p>Apart from these large-scale changes, over shorter periods weather and climate also have important impacts on Earth’s rotation, causing variations in both directions.</p>
<p>The fortnightly and monthly tidal cycles move mass around the planet, causing changes in the length of day by up to a millisecond in either direction. <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JB010830">We can see tidal variations</a> in length-of-day records over periods as long as 18.6 years. The movement of our atmosphere has a particularly strong effect, and ocean currents also play a role. Seasonal snow cover and rainfall, or groundwater extraction, alter things further. </p>
<h2>Why is Earth suddenly slowing down?</h2>
<p>Since the 1960s, when operators of radio telescopes around the planet started to devise techniques to <a href="https://www.esa.int/Science_Exploration/Space_Science/Observations_Very_Long_Baseline_Interferometry_VLBI">simultaneously observe cosmic objects like quasars</a>, we have had very precise estimates of Earth’s rate of rotation.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/59Bl8cjNg-Y?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Using radio telescopes to measure Earth’s rotation involves observations of radio sources like quasars. NASA Goddard.</span></figcaption>
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<p>A comparison between these estimates and an atomic clock has revealed a seemingly ever-shortening length of day over the past few years.</p>
<p>But there’s a surprising reveal once we take away the rotation speed fluctuations we know happen due to the tides and seasonal effects. Despite Earth reaching its shortest day on June 29 2022, the long-term trajectory seems to have shifted from shortening to lengthening since 2020. This change is unprecedented over the past 50 years.</p>
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Read more:
<a href="https://theconversation.com/we-found-the-first-australian-evidence-of-a-major-shift-in-earths-magnetic-poles-it-may-help-us-predict-the-next-155040">We found the first Australian evidence of a major shift in Earth's magnetic poles. It may help us predict the next</a>
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<p>The reason for this change is not clear. It could be due to changes in weather systems, with back-to-back La Niña events, although these have occurred before. It could be increased melting of the ice sheets, although those have not deviated hugely from their steady rate of melt in recent years. Could it be related to the huge volcano explosion in Tonga <a href="https://www.abc.net.au/news/2022-08-03/tonga-volcanic-eruption-could-temporarily-warm-the-earth/101297676#:%7E:text=A%20NASA%20study%20examining%20atmospheric,enough%20to%20worsen%20climate%20change">injecting huge amounts of water into the atmosphere</a>? Probably not, given that occurred in January 2022. </p>
<p><a href="https://www.timeanddate.com/news/astronomy/shortest-day-2022">Scientists have speculated</a> this recent, mysterious change in the planet’s rotational speed is related to a phenomenon called the “Chandler wobble” – a small deviation in Earth’s rotation axis with a period of about 430 days. Observations from radio telescopes also show that the wobble has diminished in recent years; the two may be linked. </p>
<p>One final possibility, which we think is plausible, is that nothing specific has changed inside or around Earth. It could just be long-term tidal effects working in parallel with other periodic processes to produce a temporary change in Earth’s rotation rate.</p>
<h2>Do we need a ‘negative leap second’?</h2>
<p>Precisely understanding Earth’s rotation rate is crucial for a host of applications – navigation systems such as GPS wouldn’t work without it. Also, every few years timekeepers insert leap seconds into our official timescales to make sure they don’t drift out of sync with our planet.</p>
<p>If Earth were to shift to even longer days, we may need to incorporate a “negative leap second” – this would be unprecedented, and <a href="https://arstechnica.com/science/2022/08/record-short-days-could-speed-up-debate-on-leap-seconds/">may break the internet</a>.</p>
<p>The need for negative leap seconds is regarded as unlikely right now. For now, we can welcome the news that – at least for a while – we all have a few extra milliseconds each day.</p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-could-the-earth-ever-stop-spinning-and-what-would-happen-if-it-did-174132">Curious Kids: could the Earth ever stop spinning, and what would happen if it did?</a>
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<img src="https://counter.theconversation.com/content/188147/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matt King receives funding from the Australian Research Council, the Department of Climate Change, Energy, the Environment and Water, the Department of Industry, Science and Resources, and the Australian National Collaborative Research Infrastructure Strategy (NCRIS). He has previously received funding from the Centre for Southern Hemisphere Oceans Research. </span></em></p><p class="fine-print"><em><span>Christopher Watson receives funding from the Australian National Collaborative Research Infrastructure Strategy (NCRIS) and the Australian Research Council.</span></em></p>The length of a day has critical impacts on our technologies, navigation, and more.Matt King, Director of the ARC Australian Centre for Excellence in Antarctic Science, University of TasmaniaChristopher Watson, Senior Lecturer, School of Geography, Planning, and Spatial Sciences, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1796592022-03-22T05:40:53Z2022-03-22T05:40:53ZRecord-smashing heatwaves are hitting Antarctica and the Arctic simultaneously. Here’s what’s driving them, and how they’ll impact wildlife<figure><img src="https://images.theconversation.com/files/453257/original/file-20220321-13-gfewfi.jpg?ixlib=rb-1.1.0&rect=32%2C5%2C3546%2C2591&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Windmill Islands, near Casey Research Station, Antarctica </span> <span class="attribution"><span class="source">Dana M Bergstrom</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Record-breaking heatwaves hit both Antarctica and the Arctic simultaneously this week, with temperatures reaching 47°C and 30°C higher than normal.</p>
<p>Heatwaves are bizarre at any time in Antarctica, but particularly now at the equinox as Antarctica is about to descend into winter darkness. Likewise, up north, the Arctic is just emerging from winter. </p>
<p>Are these two heatwaves linked? We don’t know yet, and it’s most likely a coincidence. But we do know weather systems in Antarctica and the Arctic are connected to regions nearest to them, and these connections sometimes reach all the way to the tropics. </p>
<p>And is climate change the cause? It might be. While it’s too soon to say for sure, we do know climate change is making polar heatwaves more common and severe, and the poles are <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Polar_regions.pdf">warming faster than the global average</a>.</p>
<p>So let’s take a closer look at what’s driving the extreme anomalies for each region, and the flow-on effects for polar wildlife like penguins and polar bears.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453486/original/file-20220322-17-1ssaemq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At this time of year, Adélie penguin chicks leave the nest to go hunting at sea on their own.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>What happened in Antarctica?</h2>
<p>Antarctica’s heatwave was driven by a slow, intense high pressure system located southeast of Australia, which carried vast amounts of warm air and moisture deep into Antarctica’s interior. It was coupled with a very intense low pressure system over the east Antarctic interior. </p>
<p>To make matters worse, cloud cover over the Antarctic ice plateau trapped heat radiating from the surface. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453484/original/file-20220322-20-183hlku.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Recent storm clouds over East Antarctica.</span>
<span class="attribution"><span class="source">Barry Becker</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Since it’s autumn in Antarctica, temperatures in the continent’s interior weren’t high enough to melt glaciers and the ice cap. But that’s not to say large swings in temperature didn’t occur. </p>
<p>For example, Vostok in the middle of the ice plateau hit a provisional high of -17.7°C (15°C higher than previous record of -32.6°C). <a href="http://www.concordiastation.aq/home-1/">Concordia</a>, the Italian-French research station also on the high plateau, experienced its highest ever temperature for any month, which was about 40°C above the March average. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Air temperature anomalies across Antarctica" src="https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453250/original/file-20220321-23-1cdkkkd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=747&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Air temperature anomalies across Antarctica at 2m above ground for the Mar 18. 2022.</span>
<span class="attribution"><span class="source">ClimateReanalyzer.org</span></span>
</figcaption>
</figure>
<p>The story is very different on the coast as rain fell, which isn’t really common for the continent.</p>
<p>The rain was <a href="https://doi.org/10.1029/2020JD033788">driven primarily by an atmospheric river</a> – a narrow band of moisture collected from warm oceans. Atmospheric rivers are found on the edge of low pressure systems and can move large amounts of water across vast distances, at scales greater than continents.</p>
<p>Despite their rarity, atmospheric rivers make an important contribution to the continent’s ice sheets, as they dump relatively large amounts of snow. When surface temperatures rise above freezing, rain rather than snow falls over Antarctica. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1504568316635107329"}"></div></p>
<p>Last Monday (March 14) air temperatures at the Australian Casey Station reached a maximum of -1.9°C. Two days later, they were more like mid-summer temperatures, reaching a new March maximum of 5.6°C, which will melt ice. </p>
<p>This is the second heatwave at Casey Station in <a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">two years</a>. In February 2020, Casey hit 9.2°C, followed by a shocking high of <a href="https://public.wmo.int/en/media/press-release/wmo-verifies-one-temperature-record-antarctic-continent-and-rejects-another">18.3°C</a> on the Antarctic Peninsula. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month</a>
</strong>
</em>
</p>
<hr>
<p>So what might this mean for wildlife?</p>
<p>Adélie penguins, which live across the entire Antarctic coastline, have recently finished their summer breeding. But thankfully, the Adélie penguin chicks had already left for sea to start hunting for food on their own, so the heatwave did not impact them. </p>
<p>The rain may have affected the local plant life, <a href="https://theconversation.com/antarcticas-moss-forests-are-drying-and-dying-103751">such as mosses</a>, especially as they were in their annual phase of drying out for the winter. But we won’t know if there’s any damage to the plants until next summer when we can visit the moss beds again.</p>
<figure class="align-center ">
<img alt="Snow at Casey Research Station March 2022" src="https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453453/original/file-20220321-14070-1skfe48.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1340&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Snow on moss beds outside Casey research station 21 March 2022.</span>
<span class="attribution"><span class="source">Chris Gallagher</span></span>
</figcaption>
</figure>
<h2>What about the Arctic?</h2>
<p>A similar weather pattern occurred last week in the Arctic. An intense low pressure system began forming off the north-east coast of the United States. An atmospheric river formed at its junction with an adjacent high pressure system. </p>
<p>This weather pattern funnelled warm air into the Arctic circle. Svalbald, in Norway, recorded a <a href="https://twitter.com/Ketil_Isaksen/status/1503740808016637953">new maximum temperature of 3.9°C</a>.</p>
<p>US researchers called the low pressure system a “<a href="https://theconversation.com/what-is-a-bomb-cyclone-an-atmospheric-scientist-explains-175825#:%7E:text=A%20bomb%20cyclone%20is%20a,24%20millibars%20in%2024%20hours">bomb cyclone</a>” because it formed so rapidly, undergoing the delightfully termed “bombogenesis”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Arctic air temperature anomalies" src="https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=595&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=595&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=595&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=747&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=747&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453251/original/file-20220321-19-1cwbkyd.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=747&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Arctic air temperature anomalies at 2 metres above the ground for March 17, 2022.</span>
<span class="attribution"><span class="source">ClimateReanalyzer.org</span></span>
</figcaption>
</figure>
<p>Winter sea ice conditions this year were already very low, and on land there was recent record-breaking <a href="https://theconversation.com/what-greenlands-record-breaking-rain-means-for-the-planet-166567">rain across Greenland</a>.</p>
<p>If the warm conditions cause sea ice to break up earlier than normal, it could have dire impacts for many animals. For example, sea ice is a crucial habitat for polar bears, enabling them to hunt seals and travel long distances.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/453485/original/file-20220322-28-1x6y3jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Early melting of Arctic ice sheets could have dire consequences for polar bears.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Many people live in the Arctic, including Arctic Indigenous people, and we know <a href="https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_CrossChapterPaper6.pdf">losing sea ice</a> disrupts subsistence hunting and cultural practices. </p>
<p>What’s more, the bomb cyclone weather system brought <a href="https://www.severe-weather.eu/global-weather/polar-vortex-2022-winter-storm-franklin-windstorm-bomb-cyclone-mk/">chaotic weather</a> to many populated areas of the Northern Hemisphere. In northern Norway, for instance, flowers have began blooming early due to three weeks of abnormally warm weather.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1505622982881853446"}"></div></p>
<h2>A harbinger for the future</h2>
<p>Modelling suggests large-scale climate patterns are become more variable. This means this seemingly one-off heatwave may be a harbinger for the future under climate change. </p>
<p>In particular, the Arctic has been warming <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Polar_regions.pdf">twice as fast</a> as the rest of the world. This is because the melting sea ice reveals more ocean beneath, and the ocean absorbs more heat as it’s darker.</p>
<p>In fact, the Intergovernmental Panel on Climate Change (IPCC) projects Arctic sea ice to continue its current retreat, with <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Polar_regions.pdf">ice-free summers</a> possible by the 2050s.</p>
<p>Antarctica’s future looks similarly concerning. The IPCC finds global warming between 2°C and 3°C this century would see the West Antarctic Ice Sheet <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Polar_regions.pdf">almost completely lost</a>. Bringing global emissions down to net zero as fast as possible will help avoid the worst impacts of climate change.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/each-antarctic-tourist-effectively-melts-83-tonnes-of-snow-new-research-177597">Each Antarctic tourist effectively melts 83 tonnes of snow – new research</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/179659/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dana Bergstrom works for the Australian Antarctic Division and is a Visiting Fellow at the University of Wollongong. Her research and fieldwork in Antarctica was supported by the Australian Antarctic Division.</span></em></p><p class="fine-print"><em><span>Sharon Robinson works for the University of Wollongong. She receives funding from the Australian Research Council and Antarctic Science Grants. She is a member of the United Nations Environment Programme Environmental Effects Assessment Panel.</span></em></p><p class="fine-print"><em><span>Simon Alexander works for the Australian Antarctic Division and is part of the Australian Antarctic Program Partnership at the University of Tasmania. His Antarctic research was supported by the Australian Antarctic Division</span></em></p>This seemingly one-off heatwave may be a harbinger for the future under climate change.Dana M Bergstrom, Principal Research Scientist, University of WollongongSharon Robinson, Professor, University of WollongongSimon Alexander, Atmospheric scientist, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1739402021-12-22T13:59:50Z2021-12-22T13:59:50ZAntarctica’s ‘doomsday’ glacier: how its collapse could trigger global floods and swallow islands<figure><img src="https://images.theconversation.com/files/438240/original/file-20211217-21-l7yfu8.jpg?ixlib=rb-1.1.0&rect=0%2C97%2C1730%2C1782&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Glaciers like Antarctica's Byrd Glacier are showing cracks and movement.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/TSKlNIgK1P4">United States Geological Survey </a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The massive Thwaites glacier in West Antarctica contains enough ice to raise global sea levels <a href="https://www.nature.com/articles/s41561-019-0510-8">by 65cm</a> if it were to completely collapse. And, worryingly, recent <a href="https://cires.colorado.edu/news/threat-thwaites-retreat-antarctica%E2%80%99s-riskiest-glacier">research suggests</a> that its long-term stability is doubtful as the glacier haemorrhages more and more ice.</p>
<p>Adding 65cm to global sea levels would be coastline-changing amounts. For context, there’s been around 20cm of sea-level <a href="https://www.nature.com/articles/s41586-020-2591-3">rise since 1900</a>, an amount that is already forcing coastal communities out of <a href="https://www.nationalgeographic.co.uk/environment-and-conservation/2021/03/sinking-land-and-rising-seas-the-dual-crises-facing-coastal">their homes</a> and exacerbating environmental problems such as flooding, saltwater contamination and habitat loss. </p>
<p>But the worry is that Thwaites, sometimes called the “doomsday glacier” because of its keystone role in the region, might not be the only glacier to go. Were it to empty into the ocean, it could trigger a regional chain reaction and drag other nearby glaciers in with it, which would mean several metres of sea-level rise. That’s because the glaciers in West Antarctica are thought to be vulnerable to a mechanism called <a href="https://www.nature.com/articles/s41467-021-23070-7">Marine Ice Cliff Instability</a> or MICI, where retreating ice exposes increasingly tall, unstable ice cliffs that collapse into the ocean.</p>
<p>A sea level rise of several metres would inundate many of the world’s <a href="https://climate-adapt.eea.europa.eu/metadata/publications/ranking-of-the-worlds-cities-to-coastal-flooding/11240357">major cities</a> – including Shanghai, New York, Miami, Tokyo and Mumbai. It would also cover huge swathes of land in coastal regions and largely swallow up low-lying island nations like Kiribati, Tuvalu and the Maldives.</p>
<h2>As big as Britain</h2>
<p>Thwaites is a frozen river of ice approximately the <a href="http://www.antarcticglaciers.org/2020/01/what-is-the-ice-volume-of-thwaites-glacier/">size of Great Britain</a>. It already contributes around 4% of the global <a href="https://thwaitesglacier.org/sites/default/files/2020-09/ThwaitesGlacierFactsSheetJune2020_1.pdf">sea-level rise</a>. Since 2000, the glacier has had a net loss of more than 1000 billion tons of ice and this has increased steadily over the last three decades. The speed of its flow has doubled <a href="https://www.sciencedirect.com/science/article/pii/S092181811630491X">in 30 years</a>, meaning twice as much ice is being spewed into the ocean as in the 1990s. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of the Amundsen sea basin including the Thwaites glacier." src="https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438239/original/file-20211217-13-1yxx0ct.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map of the Amundsen Sea Basin including the Thwaites glacier.</span>
<span class="attribution"><span class="source">European Geosciences Union</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Thwaites glacier, the widest in the world at 80 miles wide, is held back by a floating platform of ice called an ice shelf, which restrains the glacier and makes it flow less quickly. But scientists <a href="https://cires.colorado.edu/news/threat-thwaites-retreat-antarctica%E2%80%99s-riskiest-glacier">have just confirmed</a> that this ice shelf is becoming rapidly destabilised. The eastern ice shelf now has cracks criss-crossing its surface, and could collapse <a href="https://cires.colorado.edu/news/threat-thwaites-retreat-antarctica%E2%80%99s-riskiest-glacier">within ten years</a>, according to Erin Pettit, a glaciologist at Oregon State University. </p>
<p>This work supports <a href="https://www.pnas.org/content/117/40/24735">research published in 2020</a> which also noted the development of cracks and crevasses on the Thwaites ice shelf. These indicate that it is being structurally weakened. This damage can have a reinforcing feedback effect because cracking and fracturing can promote further weakening, priming the ice shelf for disintegration.</p>
<p>If Thwaites’ ice shelf did collapse, it would spell the beginning of the end for the glacier. Without its ice shelf, Thwaites glacier would discharge all its ice into the ocean over the following decades to centuries. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/aogMKvzN2x4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">New research on Thwaites glacier and its future.</span></figcaption>
</figure>
<h2>Other unstable glaciers</h2>
<p>The ice shelf – which can be thought of as the floating extension of Thwaites glacier – is one of several that scientists are watching closely in the Amundsen Sea Basin, West Antarctica. Several ice shelves that hold back glaciers there, including Thwaites and its next-door neighbour, the Pine Island glacier, are being eroded by rising ocean temperatures. </p>
<p>Warmer ocean water is able to undercut these floating ice shelves, driving melting from below that can thin the ice and weaken it, allowing the cracks and fractures that have been observed at the surface to develop. This ocean-driven melting at the bottom of the ice shelf also pushes the anchoring point where the ice meets the seabed backwards. Because the seabed slopes downwards in the Amundsen Sea, that could eventually trigger a shift as the glaciers lose their footing and retreat rapidly. </p>
<p>Ultimately, if the ice shelves retreat, it means there is less holding the West Antarctic glaciers back – allowing them to accelerate and add more to global sea levels.</p>
<p>However, scientists are still getting to grips with MICI and questions remain about the future of West Antarctic glaciers. While the collapse of Thwaites certainly could trigger a wholesale collapse event, not everyone believes this will happen. </p>
<p><a href="https://www.science.org/doi/10.1126/science.abf6271">Other work</a> suggests that the destabilisation of the Thwaites ice shelf and glacier may not lead to the kind of catastrophic outcomes that some fear. Sea ice and chunks of ice that break away from the collapsing ice shelf and glacier might have a similar restraining effect to the intact ice shelf, nipping the chain-reaction in the bud and preventing the sustained collapse of the entire West Antarctic ice sheet. </p>
<p>But while uncertainty remains about exactly what will happen in West Antarctica, one thing is for sure – the retreating Thwaites glacier will continue to add to global sea levels for many years to come.</p><img src="https://counter.theconversation.com/content/173940/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ella Gilbert does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A massive Antarctic ice shelf is showing signs of cracking and could trigger worldwide flooding.Ella Gilbert, Postdoctoral Research Associate in Climate Science, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1655612021-08-06T13:51:47Z2021-08-06T13:51:47ZRecord-breaking winter winds have blown old Arctic sea ice into the melt zone<figure><img src="https://images.theconversation.com/files/415003/original/file-20210806-23-11onvmd.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4368%2C2903&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/global-warming-arctic-north-pole-svalbard-167348594">Avatar_023/Shutterstock</a></span></figcaption></figure><p>An unusual pattern of winds drove old Arctic sea ice into a precarious position in the winter of 2020. Now in warming waters, large swathes of the Arctic’s diminishing store of old ice lie at risk of melting. But how did this happen, and why is old ice so important?</p>
<p>When winter’s darkness falls on the Arctic Ocean, temperatures plunge to below -30°C. Existing floating ice thickens as the seawater below freezes, and the ice advances into areas that were previously open water. In summer, when temperatures rise and the sun shines for months at a time, the ice thins and retreats. Each September, scientists wait and watch for the annual minimum coverage of Arctic sea ice – a useful indicator for how fast the region is changing. </p>
<p>Ice that survives the summer melt season endures for another winter. Some ice even survives several summers before finally melting. This happens particularly in the colder regions near the North Pole. Ice that survives the summer is known as perennial ice; battle-scarred from its ordeal, it ends up thicker, rougher and more resilient. It’s an important part of the climate and ecology of the Arctic and it’s disappearing due to global heating.</p>
<figure class="align-center ">
<img alt="A polar bear walks on sea ice" src="https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414905/original/file-20210805-27-12eepv8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Arctic sea ice is hunting territory for polar bears.</span>
<span class="attribution"><span class="source">Stefan Hendricks, Alfred Wegener Institute</span></span>
</figcaption>
</figure>
<p>When sunlight hits the Earth, it’s either reflected or absorbed. Reflected light bounces back into outer space, whereas absorbed light heats the planet. Sea ice covered in snow reflects up to <a href="https://nsidc.org/cryosphere/seaice/processes/albedo.html#:%7E:text=Sea%20ice%20has%20a%20much,from%20approximately%200.5%20to%200.7.">90% of incoming sunlight</a>, making it a powerful defence against global warming. But as polar sea ice melts due to climate change, sunlight increasingly hits the ocean, where over <a href="https://nsidc.org/cryosphere/seaice/processes/albedo.html#:%7E:text=Sea%20ice%20has%20a%20much,from%20approximately%200.5%20to%200.7.">90% is absorbed</a>. </p>
<p>Perennial ice is particularly important because it’s more capable of surviving the summer and shielding the Arctic Ocean from the sun and keeping the region cool. But every year the ice melt season lengthens and the growth season shortens. And both seasons in the Arctic are getting hotter. These factors conspire against perennial ice, and less has been surviving the melt season every year. </p>
<h2>Why was winter 2020-2021 so exceptional?</h2>
<p>To maintain a healthy perennial ice cover in the Arctic, it’s critical that the ice stays out of warm waters where it might melt in summer. Sea ice moves around the Arctic Ocean as it gets blown by the wind. If it stays in the cold regions, where ice can survive the summer, it has a good shot at becoming perennial ice. If the winds blow it southward into warmer waters, its chances of survival drop dramatically. </p>
<p>In February 2021, my academic colleagues and I <a href="https://www.nature.com/articles/s43247-021-00221-8">observed</a> a startling weather phenomenon in the Arctic. The polar vortex, <a href="https://www.climate.gov/news-features/understanding-climate/understanding-arctic-polar-vortex#:%7E:text=The%20Arctic%20polar%20vortex%20is,Hemisphere%20stratosphere%20in%20its%20winter.">a ring of anticlockwise-flowing wind</a> that holds a pool of extremely cold air over the Arctic, collapsed, resulting in a new record for the region’s highest surface air pressure. Cold weather then moved southwards at the surface, causing UK temperatures to fall to their <a href="https://www.theguardian.com/uk-news/2021/feb/11/uk-temperature-falls-lowest-level-decade-extreme-freeze">lowest level since 1995</a>. In Texas, extremely cold weather paralysed the power grid, leaving four million people <a href="https://www.carbonbrief.org/media-reaction-texas-deep-freeze-power-blackouts-and-the-role-of-global-warming">without power</a>. </p>
<p>In the Arctic, the breakdown of the polar vortex produced an exceptional pattern of surface winds that swirled clockwise about the centre of the Arctic Ocean like water around a plughole. These swirling winds spun the floating icepack like a spinning top. In doing so, they drove the Arctic’s perennial ice from a relatively safe and cold position north of Greenland into an area where ice increasingly can’t survive the summer: the Beaufort Sea. </p>
<p>Over the winter, the Beaufort Sea filled with perennial ice such that in the last week of February 2021, it contained a record fraction (23.5%) of the Arctic Ocean’s total perennial ice cover. This is where things get really interesting. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graph showing perennial ice cover in the 26th week of the year since 1984." src="https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414901/original/file-20210805-27-krqgx3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At 1.76 million square kilometres, perennial ice cover mid-year was lowest in 2021.</span>
<span class="attribution"><span class="source">Robbie Mallett</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Perennial ice is, in theory, resistant to melting in summer. It’s thicker, and generally has a deeper cover of protective snow on top. By positioning robust ice in an area where ice typically melts, scientists may record more ice coverage come the September minimum. But this will come at the cost of the perennial ice cover itself which, while robust, is more precarious than ever in a melt-prone region. </p>
<p>This highlights the fact that there is no single barometer for the health of Arctic sea ice. The coverage at the September minimum is important (and highly publicised) but so is the coverage of thicker, more robust perennial ice. These two metrics will probably tell different stories in September.</p>
<p>So what does the future look like for the Arctic’s old ice? As the region continues to warm at <a href="https://oaarchive.arctic-council.org/bitstream/handle/11374/2621/MMIS12_2021_REYKJAVIK_AMAP_Arctic-Climate-Change-Update-2021-Key-Trends-and-Impacts.-Summary-for-Policy-makers.pdf?sequence=1&isAllowed=y">three times</a> the global average, less and less of the ocean will become survivable for ice in summer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A line graph depicting perennial ice area with 2021 being the lowest line." src="https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414909/original/file-20210805-17-171wplo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How perennial ice area in the Arctic has changed each year since 1984.</span>
<span class="attribution"><span class="source">Robbie Mallett</span></span>
</figcaption>
</figure>
<p>Recent research using the newest generation of climate models projects that the coverage of sea ice at the September minimum will fall to conditions recognised as “ice free” <a href="https://www.nature.com/articles/s43247-021-00214-7">around 2035</a>. Since the beginning of the satellite record in 1984, the coverage of perennial ice <a href="https://iopscience.iop.org/article/10.1088/1748-9326/aade56">has roughly halved</a>, and this downward trend will continue. </p>
<p>In the last week of February 2021, the coverage of perennial ice was the second lowest on record, behind 2013. At the time of writing, using the most recent data, the perennial ice coverage has decreased substantially and now sits at the lowest level on record – its precarious positioning since winter has likely played a role. With more than a month remaining of the melt season before the September minimum, there’s lots still to play for. But it’s likely that 2021 will set a new record for the lowest perennial ice cover.</p><img src="https://counter.theconversation.com/content/165561/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robbie Mallett receives funding through the London NERC DTP.</span></em></p>A particularly stormy winter has pushed perennial sea ice into the Arctic melt zone.Robbie Mallett, PhD Candidate, London NERC DTP & Centre for Polar Observation and Modelling, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1589132021-04-14T20:09:54Z2021-04-14T20:09:54Z‘Failure is not an option’: after a lost decade on climate action, the 2020s offer one last chance<figure><img src="https://images.theconversation.com/files/394911/original/file-20210414-21-g0xgpd.jpg?ixlib=rb-1.1.0&rect=8%2C17%2C5742%2C3794&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>In May 2011, almost precisely a decade ago, the government-appointed Climate Commission released its <a href="https://www.climatecouncil.org.au/uploads/34ab075fb66ce1b08976ed1505bec7a3.pdf">inaugural report</a>. Titled The Critical Decade, the report’s final section warned that to keep global temperature rises to 2°C this century, “the decade between now and 2020 is critical”.</p>
<p>As the report noted, if greenhouse gas emissions peaked around 2011, the world’s emissions-reduction trajectory would have been easily manageable: net-zero by around 2060, and a maximum emissions reduction rate of 3.7% each year. Delaying the emissions peak by only a decade would require a trebling of this task – a maximum 9% reduction each year.</p>
<p>But, of course, the decade to 2020 did not mark the beginning of the world’s emissions-reduction journey. Global emissions <a href="https://doi.org/10.5194/essd-12-3269-2020">accelerated</a> before dropping marginally under COVID-19 restrictions, then quickly <a href="https://www.iea.org/news/after-steep-drop-in-early-2020-global-carbon-dioxide-emissions-have-rebounded-strongly">rebounding</a>.</p>
<p>Our new report, <a href="https://www.climatecouncil.org.au/resources/net-zero-emissions-plummet-decade/">released today</a>, shows the immense cost of this inaction. It is now virtually certain Earth will pass the critical 1.5°C temperature rise this century – most likely in the 2030s. Now, without delay, humanity must focus on holding warming to well below 2°C. For Australia, that means tripling its emissions reduction goal this decade to 75%. </p>
<figure class="align-center ">
<img alt="Young girl holds sign at climate protest" src="https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394910/original/file-20210414-19-13bqe54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The 2020s offer a last chance to keep warming within 2°C this century, and leave a habitable planet for future generations.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Aim high, go fast</h2>
<p>The Climate Council report is titled Aim High: Go Fast: Why Emissions Need To Plummet This Decade. It acknowledges the <a href="https://theconversation.com/earth-may-temporarily-pass-dangerous-1-5-warming-limit-by-2024-major-new-report-says-145450">multiple</a> lines of <a href="https://www.carbonbrief.org/analysis-when-might-the-world-exceed-1-5c-and-2c-of-global-warming">evidence</a> showing it will be virtually impossible to keep average global temperature rise to 1.5°C or below this century, without a period of significant overshoot and “drawdown”. (This refers to a hypothetical period in which warming exceeds 1.5°C then cools back down due to the removal of carbon dioxide (CO₂) from the atmosphere.) </p>
<p>The <a href="https://climate.nasa.gov/evidence/">increasing rate</a> of climate change, insights from past climates, and a vanishing <a href="https://climateanalytics.org/publications/2019/zero-in-on-the-remaining-carbon-budget-and-decadal-warming-rates/">carbon budget</a> all suggest the 1.5°C threshold will in fact be crossed very soon, in the 2030s.</p>
<p>There is no safe level of global warming. Already, at a global average temperature rise of <a href="https://www.carbonbrief.org/state-of-the-climate-how-the-world-warmed-in-2019">1.1°C</a>, we’re experiencing more powerful <a href="https://climate.nasa.gov/blog/2956/how-climate-change-may-be-impacting-storms-over-earths-tropical-oceans/">storms</a>, destructive <a href="http://media.bom.gov.au/social/blog/1760/explainer-what-is-a-marine-heatwave/">marine</a> and <a href="https://www.bbc.com/news/world-europe-48756480">land</a> heatwaves, and a new age of <a href="https://www.anu.edu.au/news/all-news/australia%E2%80%99s-black-summer-a-climate-wake-up-call">megafires</a>.</p>
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Read more:
<a href="https://theconversation.com/cyclone-seroja-just-demolished-parts-of-wa-and-our-warming-world-will-bring-more-of-the-same-158769">Cyclone Seroja just demolished parts of WA – and our warming world will bring more of the same</a>
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</em>
</p>
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<p>As the Intergovernmental Panel on Climate Change <a href="https://www.ipcc.ch/sr15/">has warned</a>, the consequences of breaching 1.5°C warming will be stark. Heatwaves, droughts, bushfires and intense rain events will become even more severe. Sea levels will rise, species will become extinct and crop yields will fall. Coral reefs, including the Great Barrier Reef, will decline by up to 90%.</p>
<p>And perhaps most frighteningly, overshooting 1.5°C runs a greater risk of crossing “<a href="https://www.pnas.org/content/115/33/8252">tipping points</a>”, such as the collapse of ice sheets and the release of natural carbon stores in forests and permafrost. Crossing those thresholds may set off irreversible changes to the global climate system, and destroy critical ecosystems on which life on Earth depends. </p>
<figure class="align-center ">
<img alt="An ice sheet in Greenland" src="https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394913/original/file-20210414-13-1htlheb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Climate tipping points, such as melting ice sheets, may set off irreversible changes in natural systems.</span>
<span class="attribution"><span class="source">John McConnico/AP</span></span>
</figcaption>
</figure>
<h2>Every fraction of a degree matters</h2>
<p>The outlook may be dire, but every fraction of a degree of avoided warming matters. Its value will be measured in terms of human lives, species and ecosystems saved. We can, and must, limit warming to well below 2°C. The goal is very challenging, but still achievable.</p>
<p>The strategies, technologies and pathways needed to tackle the climate challenge are <a href="https://www.climateworksaustralia.org/resource/decarbonisation-futures-solutions-actions-and-benchmarks-for-a-net-zero-emissions-australia/">now emerging</a> as fast as the risks are escalating. And in the lead-up to the COP26 climate conference in Glasgow later this year, there’s widespread momentum for international cooperation and action.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/seriously-ugly-heres-how-australia-will-look-if-the-world-heats-by-3-c-this-century-157875">Seriously ugly: here's how Australia will look if the world heats by 3°C this century</a>
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<p>Many of Australia’s strategic allies and major trading partners – including the <a href="https://theconversation.com/after-bidens-win-australia-needs-to-step-up-and-recommit-to-this-vital-un-climate-change-fund-150444">United States</a>, <a href="https://www.bbc.com/news/world-europe-55273004">Europe</a>, the <a href="https://www.gov.uk/government/news/uk-sets-ambitious-new-climate-target-ahead-of-un-summit">United Kingdom</a> and <a href="https://theconversation.com/china-just-stunned-the-world-with-its-step-up-on-climate-action-and-the-implications-for-australia-may-be-huge-147268">China</a> – are <a href="https://www.climatecouncil.org.au/climate-action-overseas-some-good-news-change/">starting to move</a> on climate change. But Australia is standing still. This is despite our nation being <a href="https://www.ipcc.ch/assessment-report/ar5/">one of the most vulnerable</a> to climate change – and despite us having some of the <a href="https://www.uts.edu.au/sites/default/files/article/downloads/ISF_100%25_Australian_Renewable_Energy_Report.pdf">world’s best</a> renewable energy resources. </p>
<p>We must urgently grab these opportunities. We propose Australia radically scale up its emissions-reduction targets – to a 75% cut by 2030 from 2005 levels (up from the current 26-28% target). Australia should also aim to reach net-zero emissions by 2035. Doing so by 2050 – a goal Prime Minister Scott Morrison says is his <a href="https://theconversation.com/scott-morrison-has-embraced-net-zero-emissions-now-its-time-to-walk-the-talk-154478">preference</a> – is too late.</p>
<figure class="align-center ">
<img alt="A coal plant" src="https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/394918/original/file-20210414-17-flf6e4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Polluting industries such as coal will have to give way to cleaner industries.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>A huge but achievable task</h2>
<p>Such dramatic action is clearly daunting. There are political, technical and other challenges ahead because action has been delayed. But a 75% emissions-reduction target is a fair and achievable contribution to the global effort. </p>
<p>Australia’s unrivalled potential for renewable energy means it can transform the electricity sector and beyond. Electric vehicles can lead to carbon-free transport and renewably generated electricity and green hydrogen can decarbonise industry. </p>
<p>The emerging new economy is <a href="https://www.climatecouncil.org.au/resources/clean-jobs-plan/">bringing jobs</a> to regional Australia and building cleaner cities by reducing fossil fuel pollution. There is staggering potential for a massive new industry built on the export to Asia of clean energy and products made from <a href="https://www.industry.gov.au/data-and-publications/australias-national-hydrogen-strategy">clean hydrogen</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/morrison-has-embraced-net-zero-emissions-its-time-to-walk-the-talk-154478">Morrison has embraced net-zero emissions – it's time to walk the talk</a>
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</em>
</p>
<hr>
<p>State, territory and local governments are <a href="https://www.theguardian.com/environment/2020/dec/02/net-zero-emissions-by-2050-target-climate-summit-president-thanks-australian-states-but-not-morrison-government">leading the way</a> in this transformation. The federal government must now join the effort.</p>
<p>The transition will no doubt be disruptive at times, and involve hard decisions. Industries such as coal will disappear and others will emerge. This will bring economic and social change which must be managed sensitively and carefully. </p>
<p>But the long-term benefits of achieving a stable climate far outweigh the short-term disruptions. As our report concludes:</p>
<blockquote>
<p>The pathway we choose now will either put us on track for a much brighter future for our children, or lock in escalating risks of dangerous climate change. The decision is ours to make. Failure is not an option.</p>
</blockquote>
<hr>
<p><em>Climate Council researcher <a href="https://www.climatecouncil.org.au/author/simon-bradshawclimatecouncil-org-au/">Dr Simon Bradshaw</a> contributed to this article.</em></p><img src="https://counter.theconversation.com/content/158913/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Will Steffen is a Councillor with the Climate Council of Australia.</span></em></p>Australia must treble its emissions reduction targets and reach net-zero emissions by 2035. Without this and other radical global action, the chance to hold warming to well below 2°C will pass us by.Will Steffen, Emeritus Professor, Fenner School of Environment & Society, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1518042021-01-28T13:08:18Z2021-01-28T13:08:18ZSea-level rise: writers imagined drowned worlds for centuries – what they tell us about the future<figure><img src="https://images.theconversation.com/files/381086/original/file-20210128-17-18gdk12.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6000%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/statue-liberty-sinks-ocean-1473010394">OFC Pictures/Shutterstock</a></span></figcaption></figure><p>Water was <a href="https://www.bloomberg.com/news/articles/2020-12-06/water-futures-to-start-trading-amid-growing-fears-of-scarcity">traded on Wall Street</a> alongside oil and gold for the first time in early December 2020. That might seem bizarre, but there is a grim logic at play. Reliable sources of water that have nourished civilisations throughout history – the glaciers and ice packs that release a steady flow each spring – are shrinking. <a href="https://tc.copernicus.org/articles/15/233/2021/">New research</a> has revealed that the world is losing ice 65% faster now than it did in the 1990s, at a rate of 1.3 trillion tonnes a year.</p>
<p>In works of <a href="https://theconversation.com/cli-fi-novels-humanise-the-science-of-climate-change-and-leading-authors-are-getting-in-on-the-act-51270">climate fiction</a>, depictions of environmental disaster often focus on the very property of water that has brought it to the attention of futures traders: its volatility. It has fed fantasies of flooded future worlds throughout history. But with the melting of the world’s ice sheets tracking the <a href="https://insideclimatenews.org/news/25012021/global-ice-loss-sea-level-rise/">worst-case scenarios</a> of scientists, the stories no longer seem so fantastical. A sea-level rise of two-and-a-half metres is possible by 2100, according to the estimates of the <a href="https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level#:%7E:text=Based%20on%20their%20new%20scenarios,above%202000%20levels%20by%202100.">National Oceanographic and Atmospheric Administration</a> in the US.</p>
<p>These predictions resonate with prophecies that have haunted cultures since the dawn of language. How might life be different in a drowned world? Who is responsible for the flood? And how can people alive today face this sea-soaked future? Literature is an inevitably rich guide.</p>
<h2>Conjuring the flood</h2>
<p>The story of a world-destroying flood reaches back in Judeo-Christian traditions to Noah’s ark and beyond that, to the Sumerian flood story that dates to around 2000 BC. This was passed down in hushed voices around campfires until it was recorded on Tablet XI of The Epic of Gilgamesh.</p>
<p>Floods occur in the myths of most cultures. The Ojibwe First Nations people in North America speak of The Great Serpent and the Great Flood; the story of Manu and Matsya is a Hindu flood myth; and the Welsh tale of Dwyvan and Dwyvach is an analogue for the son of Prometheus in Ancient Greek mythology, Deucalion, who survives the flood by building a large chest upon which to float.</p>
<figure class="align-center ">
<img alt="An illustration of Noah's Ark riding a huge wave." src="https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381092/original/file-20210128-15-1nwljve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Stories of ‘the great flood’ echo throughout cultures worldwide.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/noahs-ark-middle-storm-3d-rendering-1326289805">Fer Gregory/Shutterstock</a></span>
</figcaption>
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<p>In most of these stories, the flood is the wrath of the gods (or god) on a hedonistic or godless community, though the “good” are saved. Zeus sends a flood to punish the arrogant Pelasgians; Noah is commanded to build the ark; and Lord Vishnu, disguised as the fish-like Matsya, warns the good-hearted mortal Manu of the coming waters. Our modern preoccupations with rising seas map directly onto these stories, as we assign fault for the global warming that is melting ice caps and inching the ocean up the shore.</p>
<h2>An ocean of loneliness</h2>
<p><a href="https://theconversation.com/pandemics-from-homer-to-stephen-king-what-we-can-learn-from-literary-history-133572">Apocalyptic narratives</a> have abounded for centuries, but JG Ballard’s The Drowned World was one of the first to offer a modern interpretation of a planet beset by rising seas. Set in 2145, the influence of the 1962 novel on contemporary fiction set in a deluged future is unmistakable. Ballard imagines a balmy London that’s mostly submerged, infested with giant alligators and traversed by mercenary scuba divers who plunder the city’s museums and cathedrals. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A book cover depicting a lone figure on a rooftop surrounding by vegetation and water." src="https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1001&fit=crop&dpr=1 600w, https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1001&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1001&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1258&fit=crop&dpr=1 754w, https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1258&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/381090/original/file-20210128-19-zsqwud.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1258&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The first edition cover of The Drowned World.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/The_Drowned_World#/media/File:TheDrownedWorld(1stEd).jpg">Berkley Books</a></span>
</figcaption>
</figure>
<p>The Drowned World explores the effects of human isolation, as London is emptied of all but a few die-hard survivors, soldiers and scavengers. As separate islands, the characters wallow in the loneliness that so many of us have become used to during lockdown. Not only does the sea-level rise destroy coastal cities, it also limits emotional connections between the remnant populations. With most common ground inaccessible, Ballard projects a lonelier, more violent, world.</p>
<h2>Working together</h2>
<p>Kim Stanley Robinson’s 2017 novel New York 2140 precedes Ballard’s setting by five years, but apart from depicting cities under water, the two imagined worlds couldn’t be more different. “New York is underwater but it’s better than ever,” reads <a href="https://www.newyorker.com/books/page-turner/kim-stanley-robinsons-latest-novel-imagines-life-in-an-underwater-new-york">one review</a>. </p>
<p>Robinson moves between first and third-person narration, with several sections given over to an omniscient urban historian narrator known as “the city” or “that city smartass”. These sections describe changes in the Hudson Bay area over the last millennium, from its pre-colonisation days, through the 2008 crash, the rising seas and global disasters to the “present” day of the flooded near-future. </p>
<p>This deep-time perspective suggests that individual action for environmental repair is both futile and absolutely necessary as a form of reparation. This is the <a href="https://salvage.zone/in-print/the-limits-of-utopia/">contradiction</a> of optimistic pessimism common to speculative fiction. The individual must take political action against climate disaster, or face a drowned world alone, as Ballard’s anti-hero Kerans is doomed to. </p>
<p>Robinson’s heroes are Charlotte and Inspector Gen, two middle-aged women working in refugee resettlement and policing, respectively. They live in the same cooperative housing project in Madison Square Park as Franklin, a young futures trader manipulating water commodities. His shark-like approach to trading is altered by his community-minded neighbours, who motivate him to rebel. For Robinson, individuals can only overcome if they organise.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/EQ3oKnZx088?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>And overcoming the rising seas will mean more than adjusting to flooded coasts. Some works of fiction consider how a rise in sea level will limit food production, as in Paolo Bacigalupi’s The Windup Girl. Others depict the consequences of mass migration to the remaining habitable parts of the planet, as in EJ Swift’s The Osiris Project. </p>
<p>These stories explore a sea-level rise as an existential threat to human life that’s exacerbated by the paralysis and inaction of individuals. Recent offerings of climate fiction, such as Robinson’s New York 2140 or The Ministry for the Future go further, and operate at the level of utopian imagination implicit in Ballard’s earlier dystopian vision, asking: what if we do something about it?</p><img src="https://counter.theconversation.com/content/151804/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chelsea Haith does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Cultures worldwide are awash with tales of great floods. What can they tell us about the reality of a wetter world?Chelsea Haith, DPhil Candidate in Contemporary English Literature, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1314952020-02-12T12:39:02Z2020-02-12T12:39:02ZAncient Antarctic ice melt caused extreme sea level rise 129,000 years ago – and it could happen again<figure><img src="https://images.theconversation.com/files/314967/original/file-20200212-61966-1blj1yt.jpg?ixlib=rb-1.1.0&rect=732%2C0%2C5602%2C2311&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A blue ice area, part of the West Antarctic Ice Sheet.</span> <span class="attribution"><a class="source" href="http://www.antarcticscience.com/">Professor Chris Turney</a>, <span class="license">Author provided</span></span></figcaption></figure><p>Rising global temperatures and warming ocean waters are causing one of the world’s coldest places to melt. While we know that human activity is causing climate change and <a href="http://www.antarctica.gov.au/environment/human-impacts-in-antarctica">driving rapid changes</a> in Antarctica, the potential impacts that a warmer world would have on this region remain uncertain. Our new research might be able to provide some insight into what effect a warmer world would have in Antarctica, by looking at what happened more than 129,000 years ago. </p>
<p><a href="https://www.pnas.org/content/early/2020/02/10/1902469117">We found</a> that the mass melting of the <a href="https://www.nationalgeographic.com/environment/2019/08/west-antarctic-glaciers-melting-human-influence/">West Antarctic Ice Sheet</a> was a major cause of high sea levels during a period known as the <a href="https://skepticalscience.com/LIG1-0706.html">Last Interglacial (129,000-116,000 years ago)</a>. The extreme ice loss caused more than three metres of average global sea level rise – and worryingly, it took less than 2˚C of ocean warming for it to occur.</p>
<p>To conduct our research, we travelled to an area on the <a href="https://www.nationalgeographic.com/news/2018/06/west-antarctic-ice-sheet-collapse-climate-change/">West Antarctic Ice Sheet</a> and drilled into so-called <a href="https://eros.usgs.gov/image-gallery/image-of-the-week/antarcticas-blue-ice">blue ice areas</a> to reconstruct the glacial history of this ice sheet. </p>
<p>Blue ice areas are areas of ancient ice which have been brought to the surface by fierce, high-density winds, called <a href="https://www.weatheronline.co.uk/reports/wxfacts/Katabatic-winds.htm">katabatic winds</a>. When these winds blow over mountains, they remove the top layer of snow and erode the exposed ice. As the ice is removed by the wind, ancient ice is brought to the surface, which offers insight into the ice sheet’s history. </p>
<p>While most Antarctic researchers drill deep into the ice to extract their samples, we were able to use a technique called <a href="http://www.antarcticscience.com/climate-change.html">horizontal ice core analysis</a>. As you travel closer to the mountains of the ice sheet, the ice that been brought to the surface by these winds progressively gets older. We then were able to take surface samples on a straight, horizontal line across the blue ice area to reconstruct what happened to the ice sheet in the past. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/314968/original/file-20200212-61952-1t8gaqu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Drilling into blue ice.</span>
<span class="attribution"><a class="source" href="http://www.antarcticscience.com/">Professor Chris Turney</a>, <span class="license">Author provided</span></span>
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<p>Our team took many measurements. We first looked at the fine layers of volcanic ash in the ice to pinpoint when the mass melting took place. Alarmingly, the results showed that most ice loss happened at the start of Last Interglacial warming, some 129,000 years ago – showing how sensitive the Antarctic is to higher temperatures. We think it’s likely this melting started well before the ocean warmed by 2˚C. This is concerning to us today, as ocean temperatures continue to increase, and <a href="http://imbie.org/wp-content/uploads/2018/06/18_IMBIE_2018_1.10_HD.mp4">the West Antarctic is already melting</a>.</p>
<p>We also measured <a href="http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/">temperature-sensitive water molecules</a> across the blue ice area. These isotopes revealed a large shift in temperatures, highlighting a major gap in our record at the start of the Last Interglacial. This indicates a period of sustained ice loss over thousands of years. </p>
<p>This period of missing ice coincides with extreme sea level rise, suggesting rapid ice melt from the West Antarctic Ice Sheet. DNA testing of ancient microbes preserved in the ice revealed an abundance of methane-consuming bacteria. Their presence suggests that the release of methane gases from sediments under the ice sheet may have also played a <a href="https://www.nationalgeographic.com/news/2012/8/120831-antarctica-methane-global-warming-science-environment/">role in accelerating the warming process</a>.</p>
<p>The West Antarctic ice sheet can tell us a lot about the effect of warming ocean temperatures because it <a href="https://www.bbc.com/news/science-environment-51097309">rests on the seabed</a>. It’s surrounded by large areas of floating ice, called ice shelves, that protect the central part of the sheet. As warmer ocean water travels into cavities beneath the ice shelves, ice melts from below, thinning the shelves and making the central sheet highly vulnerable to warming ocean temperatures. This process is currently being researched on the West Antarctic Thwaites Glacier, nicknamed <a href="https://www.youtube.com/watch?v=f0AWsJ0cmLE">the “Doomsday Glacier”</a>. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/why-remote-antarctica-is-so-important-in-a-warming-world-88197">Why remote Antarctica is so important in a warming world</a>
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<p>Using data from our fieldwork, we ran model simulations to investigate how warming might affect the floating ice shelves. These ice shelves protect the ice sheets and help slow the flow of ice off the continent. Our results suggest a 3.8 metre sea level rise during the first thousand years of a 2˚C warmer ocean. Most of the modelled sea level rise occurred after the loss of the ice shelves, which collapsed within the first two hundred years of higher temperatures. </p>
<p>These findings are worrying – especially if persistent high sea surface temperatures could prompt the larger East Antarctic Ice Sheet to melt, driving global sea levels even higher. But our findings suggest the West Antarctic Ice Sheet may be <a href="https://theconversation.com/tipping-point-how-we-predict-when-antarcticas-melting-ice-sheets-will-flood-the-seas-56125">close to a tipping point</a>. Only a small temperature increase could trigger abrupt ice sheet melt and a multi-metre rise in global sea levels. </p>
<p>At the moment, research suggests that global sea levels could <a href="https://www.ipcc.ch/report/ar5/wg1/">rise between 45-82cm</a> over the next century. However, it’s thought that Antarctica will only contribute around 5cm of this – most of this sea level rise will be caused by warmer ocean waters and the melting of the Greenland Ice Sheet. But based on our findings, Antarctica’s contribution could be much greater than anticipated. </p>
<p>Despite 197 countries committing under the Paris agreement to <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">restricting global warming</a> to 2˚C by the end of this century, our findings show that even minor increases in temperature could have <a href="https://theconversation.com/why-remote-antarctica-is-so-important-in-a-warming-world-88197">far-reaching impacts</a>. </p>
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<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1131495">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/131495/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Fogwill receives funding from the Australian Research Council and Innovate UK. </span></em></p><p class="fine-print"><em><span>Chris Turney receives funding from the Australian Research Council (ARC). Chris is a science advisor for clean-tech firm CarbonScape (<a href="http://www.carbonscape.com">www.carbonscape.com</a>)</span></em></p><p class="fine-print"><em><span>Zoë Thomas receives funding from the Australian Research Council (ARC).</span></em></p>Our research shows the Antarctic could be closer to a tipping point than previously thought.Chris Fogwill, Professor of Glaciology and Palaeoclimatology, Keele UniversityChristian Turney, Professor of Earth Science and Climate Change, ARC Centre of Excellence for Australian Biodiversity and Heritage, UNSW SydneyZoë Thomas, ARC DECRA Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1198222019-07-11T20:16:24Z2019-07-11T20:16:24ZArctic ice loss is worrying, but the giant stirring in the South could be even worse<figure><img src="https://images.theconversation.com/files/283039/original/file-20190708-51288-knzf75.jpeg?ixlib=rb-1.1.0&rect=930%2C0%2C5720%2C2530&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Field camp on the East Antarctic ice sheet</span> <span class="attribution"><span class="source">Nerilie Abram</span></span></figcaption></figure><p>A <a href="http://nsidc.org/greenland-today/2019/07/a-record-melt-event-in-mid-june/">record start to summer ice melt in Greenland</a> this year has drawn attention to the northern ice sheet. We will have to wait to see if 2019 continues to break ice-melt records, but in the rapidly warming Arctic the <a href="https://theconversation.com/time-will-tell-if-this-is-a-record-summer-for-greenland-ice-melt-but-the-pattern-over-the-past-20-years-is-clear-119307">long-term trends of ice loss are clear</a>. </p>
<p>But what about at the other icy end of the planet?</p>
<p><a href="https://theconversation.com/antarctica-has-lost-nearly-3-trillion-tonnes-of-ice-since-1992-98259">Antarctica is an icy giant</a> compared to its northern counterpart. The water frozen in the Greenland ice sheet is equivalent to around 7 metres of potential sea level rise. In the Antarctic ice sheet there are around 58 metres of sea-level rise currently locked away. </p>
<p>Like Greenland, the Antarctic ice sheet is losing ice and contributing to unabated global sea level rise. But there are worrying signs Antarctica is changing faster than expected and in places previously thought to be protected from rapid change.</p>
<h2>The threat from beneath</h2>
<p>On the Antarctic Peninsula – the most northerly part of the Antarctic continent – air temperatures over the past century have risen faster than any other place in the Southern Hemisphere. Summer melting already happens on the Antarctic Peninsula between 25 and 80 days each year. The number of melt days will rise by at least 50% when global warming hits the <a href="https://www.frontiersin.org/articles/10.3389/fenvs.2019.00102/full">soon-to-be-reached 1.5°C limit</a> set out in the Paris Agreement, with some predictions pointing to as much as a 150% increase in melt days. </p>
<p>But the main threat to the Antarctic ice sheet doesn’t come from above. What threatens to truly transform this vast icy continent lies beneath, where warming ocean waters (and the vast heat carrying capacity of seawater) have the potential to melt ice at an unprecedented rate. </p>
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Read more:
<a href="https://theconversation.com/new-findings-on-ocean-warming-5-questions-answered-106215">New findings on ocean warming: 5 questions answered</a>
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<p>Almost all (<a href="https://theconversation.com/new-findings-on-ocean-warming-5-questions-answered-106215">around 93%</a>) of the extra heat human activities have caused to accumulate on Earth since the Industrial Revolution lies within the ocean. And a large majority of this has been taken into the depths of the Southern Ocean. It is thought that <a href="https://theconversation.com/climate-shenanigans-at-the-ends-of-the-earth-why-has-sea-ice-gone-haywire-69485">this effect could delay the start of significant warming</a> over much of Antarctica for a century or more.</p>
<p>However, the Antarctic ice sheet has a weak underbelly. In some places the ice sheet sits on ground that is below sea level. This puts the ice sheet in direct contact with warm ocean waters that are very effective at melting ice and destabilising the ice sheet. </p>
<p>Scientists have <a href="https://www.cambridge.org/core/journals/journal-of-glaciology/article/weak-underbelly-of-the-west-antarctic-ice-sheet/61C4BC23CCF0106FDBC00502BF2291BF">long been worried about the potential weakness of ice in West Antarctica</a> because of its deep interface with the ocean. This concern was flagged in the first report of the Intergovernmental Panel on Climate Change (IPCC) way back in 1990, although it was also thought that substantial ice loss from Antarctica wouldn’t be seen this century. Since 1992 satellites have been monitoring the status of the Antarctic ice sheet and we now know that not only is ice loss already underway, it is also vanishing at an accelerating rate.</p>
<p>The <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082182">latest estimates</a> indicate that 25% of the West Antarctic ice sheet is now unstable, and that Antarctic ice loss has increased five-fold over the past 25 years. These are remarkable numbers, bearing in mind that more than 4 metres of global sea-level rise are locked up in the West Antarctic alone.</p>
<iframe src="https://giphy.com/embed/Q8C80FC38iXjcQLpfG" width="100%" height="312" frameborder="0" class="giphy-embed" allowfullscreen=""></iframe>
<p><a href="https://giphy.com/gifs/Q8C80FC38iXjcQLpfG">Antarctic ice loss 1992–2019, European Space Agency.</a></p>
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<strong>
Read more:
<a href="https://theconversation.com/antarctica-has-lost-nearly-3-trillion-tonnes-of-ice-since-1992-98259">Antarctica has lost nearly 3 trillion tonnes of ice since 1992</a>
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<p>Thwaites Glacier in West Antarctica is currently the focus of a <a href="https://thwaitesglacier.org/">major US-UK research program</a> as there is still a lot we don’t understand about how quickly ice will be lost here in the future. For example, gradual lifting of the bedrock as it responds to the lighter weight of ice (known as <a href="https://theconversation.com/the-west-antarctic-ice-sheet-is-in-trouble-but-the-ground-beneath-it-may-buy-some-time-98368">rebounding</a>) could reduce contact between the ice sheet and warm ocean water and help to stabilise runaway ice loss. </p>
<p>On the other hand, <a href="https://www.nature.com/articles/s41586-019-0889-9">melt water from the ice sheets</a> is changing the structure and circulation of the Southern Ocean in a way that could bring even warmer water into contact with the base of the ice sheet, further amplifying ice loss.</p>
<p>There are other parts of the Antarctic ice sheet that haven’t had this same intensive research, but which appear to now be stirring. The <a href="https://www.anu.edu.au/news/all-news/new-satellites-show-worrying-view-of-droughts-and-ice-loss">Totten Glacier</a>, close to Australia’s Casey station, is one area unexpectedly losing ice. There is a very pressing need to understand the vulnerabilities here and in other remote parts of the East Antarctic coast.</p>
<h2>The other type of ice</h2>
<p><a href="https://theconversation.com/cold-and-calculating-what-the-two-different-types-of-ice-do-to-sea-levels-59996">Sea ice</a> forms and floats on the surface of the polar oceans. The decline of Arctic sea ice over the past 40 years is one of the most visible climate change impacts on Earth. But recent years have shown us that the behaviour of Antarctic sea ice is stranger and potentially more volatile.</p>
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<p><a href="https://giphy.com/gifs/fveoHoYLH4oG1D0ZVJ"></a></p>
<p>The extent of sea ice around Antarctica has been gradually increasing for decades. This is <a href="https://theconversation.com/record-high-to-record-low-what-on-earth-is-happening-to-antarcticas-sea-ice-66114">contrary to expectations from climate simulations</a>, and has been attributed to changes in the ocean structure <a href="https://www.nature.com/articles/ncomms10409">and changing winds circling the Antarctic continent</a>. </p>
<p>But in 2015, the amount of sea ice around Antarctica <a href="https://www.pnas.org/content/early/2019/06/25/1906556116">began to drop precipitously</a>. In just 3 years Antarctica lost the same amount of sea ice the Arctic lost in 30.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-antarcticas-sea-ice-cover-is-so-low-and-no-its-not-just-about-climate-change-109572">Why Antarctica's sea ice cover is so low (and no, it's not just about climate change)</a>
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<p>So far in 2019, <a href="https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/">sea ice around Antarctica is tracking</a> near or below the lowest levels on record from 40 years of satellite monitoring. In the long-term this trend is expected to continue, but such a dramatic drop over only a few years was not anticipated. </p>
<p>There is still a lot to learn about how quickly Antarctica will respond to climate change. But there are very clear signs that the icy giant is awakening and – via global sea level rise – coming to pay us all a visit.</p><img src="https://counter.theconversation.com/content/119822/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nerilie Abram receives funding from the Australian Research Council through the Centre of Excellence for Climate Extremes and a Future Fellowship, and from the Department of Environment. </span></em></p><p class="fine-print"><em><span>Matthew England receives funding from the Australian Research Council, the Earth Science and Climate Change Hub of the Australian Government's National Environmental Science Programme (NESP) and the Centre for Southern Hemisphere Oceans Research (CSHOR).
</span></em></p><p class="fine-print"><em><span>Matt King receives funding from Australian Research Council, Department of Environment and the Centre for Southern Hemisphere Oceans Research (CSHOR).
</span></em></p>Some 58 metres of sea level rise is locked up in Antartica’s ice sheets, and it’s melting faster than expected.Nerilie Abram, ARC Future Fellow, Research School of Earth Sciences; Chief Investigator for the ARC Centre of Excellence for Climate Extremes, Australian National UniversityMatthew England, Australian Research Council Laureate Fellow; Deputy Director of the Climate Change Research Centre (CCRC); Chief Investigator in the ARC Centre of Excellence in Climate System Science, UNSW SydneyMatt King, Professor, Surveying & Spatial Sciences, School of Technology, Environments and Design, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1167532019-05-20T20:59:09Z2019-05-20T20:59:09ZClimate change: sea level rise could displace millions of people within two generations<figure><img src="https://images.theconversation.com/files/273866/original/file-20190510-183093-1ageusy.JPG?ixlib=rb-1.1.0&rect=0%2C0%2C3648%2C2736&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A small boat in the Illulissat Icefjord is dwarfed by the icebergs that have calved from the floating tongue of Greenland's largest glacier, Jacobshavn Isbrae</span> <span class="attribution"><span class="source">Michael Bamber</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Antarctica is further from civilisation than any other place on Earth. The Greenland ice sheet is closer to home but around one tenth the size of its southern sibling. Together, these two ice masses hold enough frozen water to raise global mean sea level by 65 metres if they were to suddenly melt. But how likely is this to happen?</p>
<p>The Antarctic ice sheet is around one and half times larger than Australia. What’s happening in one part of Antarctica may not be the same as what’s happening in another – just like the east and west coasts of the US can experience very different responses to, for example, <a href="https://www.climate.gov/news-features/blogs/enso/united-states-el-ni%C3%B1o-impacts-0">a change in the El Niño weather pattern</a>. These are periodic climate events that result in wetter conditions across the southern US, warmer conditions in the north and drier weather on the north-eastern seaboard. </p>
<p>The ice in Antarctica is nearly 5km thick in places and we have very little idea what the conditions are like at the base, even though those conditions play a key role in determining the speed with which the ice can respond to climate change, including how fast it can flow toward and into the ocean. A warm, wet base lubricates the bedrock of land beneath the ice and allows it to slide over it.</p>
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<img alt="" src="https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275395/original/file-20190520-69192-1kfaj5d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Though invisible from the surface, melting within the ice can speed up the process by which ice sheets slide towards the sea.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/glacier-serpimolot-bay-bear-on-northern-384912739">Gans33/Shutterstock</a></span>
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<p>These issues have made it particularly difficult to produce model simulations of how ice sheets will respond to climate change in future. Models have to capture all the processes and uncertainties that we know about and those that we don’t – the “known unknowns” and the “unknown unknowns” as <a href="https://www.youtube.com/watch?v=GiPe1OiKQuk">Donald Rumsfeld once put it</a>. As a result, several recent studies suggest that previous Intergovernmental Panel on Climate Change reports may have <a href="https://science.sciencemag.org/content/354/6318/1375">underestimated how much</a> melting ice sheets will contribute to sea level in future.</p>
<h2>What the experts say</h2>
<p>Fortunately, models are not the only tools for predicting the future. <a href="https://www.nature.com/articles/nclimate1778">Structured Expert Judgement</a> is a method from a study one of us published in 2013. Experts give their judgement on a hard-to-model problem and their judgements are combined in a way that takes into account how good they are at <a href="https://www.nature.com/articles/463294a">assessing their own uncertainty</a>. This provides a rational consensus.</p>
<p>The approach has been used when the consequences of an event are potentially catastrophic, but our ability to model the system is poor. These include volcanic eruptions, earthquakes, the spread of vector-borne diseases such as malaria and even aeroplane crashes. </p>
<p><a href="https://www.nature.com/articles/nclimate1778">Since the study in 2013</a>, scientists modelling ice sheets have improved their models by trying to incorporate processes that cause positive and negative feedback. Impurities on the surface of the Greenland ice sheet cause positive feedback as they enhance melting by absorbing more of the sun’s heat. The stabilising effect of bedrock rising as the overlying ice thins, lessening the weight on the bed, is an example of negative feedback, as it slows the rate that the ice melts. </p>
<p>The record of observations of ice sheet change, primarily from satellite data, has also grown in length and quality, helping to <a href="https://iopscience.iop.org/article/10.1088/1748-9326/aac2f0/pdf">improve knowledge of the recent behaviour of the ice sheets</a>.</p>
<p>With colleagues from the UK and US, we undertook <a href="https://www.pnas.org/cgi/doi/10.1073/pnas.1817205116">a new Structured Expert Judgement exercise</a>. With all the new research, data and knowledge, you might expect the uncertainties around how much ice sheet melting will contribute to sea level rise to have got smaller. Unfortunately, that’s not what we found. What we did find was a range of future outcomes that go from bad to worse.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=271&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=271&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=271&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274936/original/file-20190516-69182-1oa09zo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=340&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Reconstructed sea level for the last 2500 years. Note the marked increase in rate since about 1900 that is unprecedented over the whole time period.</span>
<span class="attribution"><a class="source" href="https://www.pnas.org/content/113/11/E1434.short">Robert Kopp/Kopp et al. (2016)</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Rising uncertainty</h2>
<p>We gathered together 22 experts in the US and UK in 2018 and combined their judgements. The results are sobering. Rather than a shrinking in the uncertainty of future ice sheet behaviour over the last six years, it has grown.</p>
<p>If the global temperature increase stays below 2°C, the experts’ best estimate of the average contribution of the ice sheets to sea level was 26cm. They concluded, however, that there is a 5% chance that the contribution could be as much as 80cm. </p>
<p>If this is combined with the two other main factors that influence sea level – glaciers melting around the world and the expansion of ocean water as it warms – then global mean sea level rise could exceed one metre by 2100. If this were to occur, many small island states would experience their current once-in-a-hundred–year <a href="https://advances.sciencemag.org/content/4/4/eaap9741">flood every other day and become effectively uninhabitable</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275396/original/file-20190520-69195-2c9dga.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A climate refugee crisis could dwarf all previous forced migrations.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lesbos-greece-september-30-2015-refugees-325232699?src=WxHLErac17sJTjerJLHYXA-1-7">Punghi/Shutterstock</a></span>
</figcaption>
</figure>
<p>For a climate change scenario closer to business as usual – where our current trajectory for economic growth continues and global temperatures increase by 5°C – the outlook is even more bleak. The experts’ best estimate average in this case is 51cm of sea level rise caused by melting ice sheets by 2100, but with a 5% chance that global sea level rise could exceed two metres by 2100. That has the potential to <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsta.2010.0291">displace some 200m people</a>. </p>
<p>Let’s try and put this into context. The Syrian refugee crisis is estimated to have caused <a href="http://data.unhcr.org/syrianrefugees/asylum.php">about a million people to migrate to Europe</a>. This occurred over years rather than a century, giving much less time for countries to adjust. Still, sea level rise driven by migration of this size might threaten the existence of nation states and result in unimaginable stress on resources and space. There is time to change course, but not much, and the longer we delay the harder it gets, the bigger the mountain we have to climb.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1116753">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/116753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Bamber receives funding from the UK Natural Environment Research Council, The Royal Society and the European Research Council. </span></em></p><p class="fine-print"><em><span>Michael Oppenheimer receives funding from US National Science Foundation and the High Meadows Foundation. He is affiliated with the Environmental Defense Fund, Climate Central, and the Climate Science Legal Defense Fund.
</span></em></p>Sea levels could rise by two metres by 2100, sparking a refugee crisis unlike anything the world has ever seen.Jonathan Bamber, Professor of Physical Geography, University of BristolMichael Oppenheimer, Professor of Geosciences and International Affairs, Princeton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1113452019-02-10T19:14:11Z2019-02-10T19:14:11ZMelting Himalayan glaciers: a big drop in a bucket that’s already full<p>A <a href="https://link.springer.com/book/10.1007%2F978-3-319-92288-1">new report</a> has warned that even if global warming is held at 1.5°C, we will still lose a third of the glaciers in the Hindu Kush-Himalaya (HKH) region. What does that mean for rivers that flow down these mountains, and the people who depend on them? </p>
<p>The HKH region is home to the tallest mountains on Earth, and also to the source of rivers that sustain close to 2 billion people. These rivers supply agriculture with water and with sediments that fertilise soils in valleys and the floodplain. </p>
<p>Some of these rivers are hugely culturally significant. The Ganges (or Ganga), for instance, which flows for more than 2,525km from the western Himalayas into the Bay of Bengal, is personified in Hinduism as the goddess Gaṅgā. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257843/original/file-20190207-174857-jk1rf2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Ganga River at Rishikesh, as it exits the Himalayas.</span>
<span class="attribution"><span class="source">Anthony Dosseto</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/warm-ice-in-mount-everests-glaciers-makes-them-more-sensitive-to-climate-change-new-research-107325">Warm ice in Mount Everest's glaciers makes them more sensitive to climate change – new research</a>
</strong>
</em>
</p>
<hr>
<h2>When it rains, it pours… literally</h2>
<p>Before we get to the effect of melting glaciers on Himalayan rivers, we need to understand where they get their water.</p>
<p>For much of Himalayas, rain falls mostly during the monsoon active between June and September. The monsoon brings heavy rain and often causes <a href="https://www.youtube.com/watch?time_continue=99&v=QxoMqrjzM5E">devastating floods</a>, such as in <a href="https://www.theguardian.com/world/2013/jun/24/india-uttarakhand-floods-rescue-death-toll">northern India in 2013</a>, which forced the evacuation of more than 110,000 people.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/SjGGjywq8Fo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">2013 floods in Uttarakhand, India.</span></figcaption>
</figure>
<p>But the summer monsoon is not the only culprit for devastating floods. Landslides can dam the river, and when this dam bursts it can cause dramatic, unpredictable flooding. Some of those events have been linked to folk stories of floods in <a href="https://theconversation.com/geomythology-can-geologists-relate-ancient-stories-of-great-floods-to-real-events-63434">many cultures around the world</a>. In the Himalayas, a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379113002874">study</a> tracking the 1,000-year history of large floods showed that heavy rainfall and landslide-dam burst are the main causes.</p>
<p>When they melt, glaciers can also create natural dams, which can then burst and send floods down the valley. In this way, the newly forecast melting poses an acute threat.</p>
<p>The potential problem is worsened still further by the Intergovernmental Panel on Climate Change’s <a href="https://www.ipcc.ch/report/managing-the-risks-of-extreme-events-and-disasters-to-advance-climate-change-adaptation">prediction</a> that the frequency of extreme rainfall events will also increase.</p>
<h2>Come hell or high water</h2>
<p>What will happen to Himalayan rivers when the taps are turned to high in this way? To answer this, we need to look into the past. </p>
<p>For tens of thousands of years, rivers have polished rocks and laid down sediments in the lower valleys of the mountain range. These sediments and rocks tell us the story of how the river behaves when the tap opens or closes.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257845/original/file-20190207-174894-ksaduy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rock surfaces tell us where the river was carving into its bed.</span>
<span class="attribution"><span class="source">Anthony Dosseto</span></span>
</figcaption>
</figure>
<p>Some experts <a href="https://pubs.geoscienceworld.org/gsa/geology/article-abstract/30/10/911/192283/impulsive-alluviation-during-early-holocene">propose</a> that intense rain tends to trigger landslides, choking the river with sediments which are then dumped in the valleys. Others <a href="https://www.sciencedirect.com/science/article/abs/pii/S027737911000168X">suggest</a> that the supply of sediments to the river generally doesn’t change much even in extreme rainfall events, and that the main effect of the extra flow is that the river erodes further into its bed.</p>
<p>The <a href="https://www.sciencedirect.com/science/article/abs/pii/S0277379118300325">most recent work</a> supports the latter theory. It found that 25,000-35,000 years ago, when the monsoon was much weaker than today, sediments were filling up Himalayan valleys. But more recently (3,000-6,000 years ago), rock surfaces were exposed during a period of strong monsoon, illustrating how the river carved into its bed in response to higher rainfall.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/257846/original/file-20190207-174870-3o7iha.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sediments laid down in Himalayan valleys support agriculture, but also tell us the ancient story of rivers that carried them.</span>
<span class="attribution"><span class="source">Anthony Dosseto</span></span>
</figcaption>
</figure>
<p>So what does the past tell us about the future of Himalayan rivers? More frequent extreme rainfall events mean more floods, of course. But a stronger monsoon also means rivers will cut deeper into their beds, instead of fertilising Himalayan valleys and the <a href="https://en.wikipedia.org/wiki/Indo-Gangetic_Plain">Indo-Gangetic plain</a> with sediments.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/devastating-himalayan-floods-are-made-worse-by-an-international-blame-game-83103">Devastating Himalayan floods are made worse by an international blame game</a>
</strong>
</em>
</p>
<hr>
<p>What about glaciers melting? For as long as there are glaciers, this will increase the amount of meltwater in the rivers each spring (until 2060, according the <a href="https://link.springer.com/book/10.1007%2F978-3-319-92288-1">report</a>, after which there won’t be any meltwater to talk about). So this too will contribute to rivers carving into their beds instead of distributing sediments. It will also increase the risk of flooding from outburst of glacial lake dams.</p>
<p>So what is at stake? The melting glaciers? No. Given thousands or millions of years, it seems likely that they will one day return. But on a more meaningful human timescale, what is really at stake is us – our own survival. Global warming is reducing our resources, and making life more perilous along the way. The rivers of the Himalayas are just one more example.</p><img src="https://counter.theconversation.com/content/111345/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anthony Dosseto receives funding from the Australian Research Council.</span></em></p>A new report predicts that one-third of the ice in the Himalayas will melt, even if we contain global warming to 1.5C. So what does that mean for the flood-prone valleys below?Anthony Dosseto, Associate Professor, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/837762017-09-12T19:41:44Z2017-09-12T19:41:44ZHow Antarctic ice melt can be a tipping point for the whole planet’s climate<figure><img src="https://images.theconversation.com/files/185599/original/file-20170912-26996-15apq9m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Melting Antarctic ice can trigger effects on the other side of the globe.</span> <span class="attribution"><span class="source">NASA/Jane Peterson</span></span></figcaption></figure><p>Melting of Antarctica’s ice can trigger rapid warming on the other side of the planet, according to our <a href="https://www.nature.com/articles/s41467-017-00577-6">new research</a> which details how just such an abrupt climate event happened 30,000 years ago, in which the North Atlantic region warmed dramatically.</p>
<p>This idea of “tipping points” in Earth’s system has had something of a bad rap ever since the 2004 blockbuster <a href="http://www.imdb.com/title/tt0319262/">The Day After Tomorrow</a> purportedly showed how melting polar ice can trigger all manner of global changes.</p>
<p>But while the movie certainly exaggerated the speed and severity of abrupt climate change, we do know that many natural systems are vulnerable to being pushed into different modes of operation. The melting of Greenland’s ice sheet, the retreat of Arctic summer sea ice, and the collapse of the global ocean circulation are all examples of potential vulnerability in a future, warmer world.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/chasing-ice-how-ice-cores-shape-our-understanding-of-ancient-climate-55235">Chasing ice: how ice cores shape our understanding of ancient climate</a>
</strong>
</em>
</p>
<hr>
<p>Of course it is notoriously hard to predict when and where elements of Earth’s system will abruptly tip into a different state. A key limitation is that historical climate records are often too short to test the skill of our computer models used to predict future environmental change, hampering our ability to plan for potential abrupt changes. </p>
<p>Fortunately, however, <a href="http://www.sciencedirect.com/science/article/pii/S0277379116303766">nature preserves a wealth of evidence in the landscape that allows us to understand how longer time-scale shifts can happen</a>.</p>
<h2>Core values</h2>
<p>One of the most important sources of information on past climate tipping points are the kilometre-long cores of ice drilled from the Greenland and Antarctic ice sheets, which preserve exquisitely detailed information <a href="https://theconversation.com/the-three-minute-story-of-800-000-years-of-climate-change-with-a-sting-in-the-tail-73368">stretching back up to 800,000 years</a>. </p>
<p>The Greenland ice cores record <a href="http://onlinelibrary.wiley.com/doi/10.1002/2015GL066344/full">massive, millennial-scale swings in temperature</a> that have occurred across the North Atlantic region over the past 90,000 years. The scale of these swings is staggering: in some cases temperatures rose by 16°C in just a few decades or even years.</p>
<p>Twenty-five of these major so-called <a href="https://www.ncdc.noaa.gov/abrupt-climate-change/Heinrich%20and%20Dansgaard%E2%80%93Oeschger%20Events">Dansgaard–Oeschger (D-O) warming events</a> have been identified. These abrupt swings in temperature happened too quickly to have been caused by Earth’s slowly changing orbit around the Sun. Fascinatingly, when ice cores from Antarctica are compared with those from Greenland, we see a “seesaw” relationship: when it warms in the north, the south cools, and vice versa.</p>
<p>Attempts to explain the cause of this bipolar seesaw have traditionally focused on the North Atlantic region, and include melting ice sheets, changes in ocean circulation or wind patterns.</p>
<p>But as our new research shows, these might not be the only cause of D-O events.</p>
<p>Our new paper, <a href="https://www.nature.com/articles/s41467-017-00577-6">published today in Nature Communications</a>, suggests that another mechanism, with its origins in Antarctica, has also contributed to these rapid seesaws in global temperature.</p>
<h2>Tree of knowledge</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185597/original/file-20170912-28358-gzsv1v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 30,000-year-old key to climate secrets.</span>
<span class="attribution"><span class="source">Chris Turney</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We know that there have been <a href="http://science.sciencemag.org/content/sci/288/5472/1815.full.pdf?ck=nck">major collapses of the Antarctic ice sheet in the past</a>, raising the possibility that these may have tipped one or more parts of the Earth system into a different state. To investigate this idea, we analysed an ancient New Zealand kauri tree that was extracted from a peat swamp near Dargaville, Northland, and which lived between 29,000 and 31,000 years ago. </p>
<p>Through accurate dating, we know that this tree lived through a short D-O event, during which (as explained above) temperatures in the Northern Hemisphere would have risen. Importantly, the unique pattern of atmospheric radioactive carbon (or carbon-14) found in the tree rings allowed us to identify similar changes preserved in climate records from ocean and ice cores (the latter using beryllium-10, an isotope formed by similar processes to carbon-14). This tree thus allows us to compare directly what the climate was doing during a D-O event beyond the polar regions, providing a global picture.</p>
<p>The extraordinary thing we discovered is that the warm D-O event coincided with a 400-year period of surface cooling in the south and <a href="http://science.sciencemag.org/content/sci/288/5472/1815.full.pdf?ck=nck">a major retreat of Antarctic ice</a>. </p>
<p>When we searched through other climate records for more information about what was happening at the time, we found no evidence of a change in ocean circulation. Instead we found a collapse in the rain-bearing Pacific trade winds over tropical northeast Australia that was coincident with the 400-year southern cooling. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/two-centuries-of-continuous-volcanic-eruption-may-have-triggered-the-end-of-the-ice-age-83420">Two centuries of continuous volcanic eruption may have triggered the end of the ice age</a>
</strong>
</em>
</p>
<hr>
<p>To explore how melting Antarctic ice might cause such dramatic change in the global climate, we used a climate model to simulate the release of large volumes of freshwater into the Southern Ocean. The model simulations all showed the same response, in agreement with our climate reconstructions: regardless of the amount of freshwater released into the Southern Ocean, the surface waters of the tropical Pacific nevertheless warmed, causing changes to wind patterns that in turn triggered the North Atlantic to warm too. </p>
<p>Future work is now focusing on what caused the Antarctic ice sheets to retreat so dramatically. Regardless of how it happened, it looks like melting ice in the south can drive abrupt global change, something of which we should be aware in a future warmer world.</p><img src="https://counter.theconversation.com/content/83776/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Chris Turney receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Jonathan Palmer receives funding from the Australian Research Council (ARC). </span></em></p><p class="fine-print"><em><span>Peter Kershaw has received fundng from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Steven Phipps receives funding from the Australian Antarctic Science Program, the Australian Research Council, the International Union for Quaternary Research, the National Computational Infrastructure Merit Allocation Scheme, the New Zealand Marsden Fund, the University of Tasmania and UNSW Australia.</span></em></p><p class="fine-print"><em><span>Zoe Thomas receives funding from the Australian Research Council. </span></em></p>The climate secrets contained in an ancient tree that lived through abrupt global change reveal how Antarctica can trigger rapid warming in the north by dumping cold water into the Southern Ocean.Christian Turney, Professor of Earth Sciences and Climate Change, UNSW SydneyJonathan Palmer, Research Fellow, School of Biological, Earth and Environmental Sciences., UNSW SydneyPeter Kershaw, Emeritus Professor, Earth, Atmosphere and Environment, Monash UniversitySteven Phipps, Palaeo Ice Sheet Modeller, University of TasmaniaZoë Thomas, Research Associate, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/801402017-06-28T20:10:02Z2017-06-28T20:10:02ZThe winners and losers of Antarctica’s great thaw<figure><img src="https://images.theconversation.com/files/175983/original/file-20170628-25828-p9y5t1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Adélie penguin at the Mt Siple breeding colony, West Antarctica.</span> <span class="attribution"><span class="source">Jasmine Lee</span>, <span class="license">Author provided</span></span></figcaption></figure><p>When you think of Antarctica, you probably picture vast, continuous ice sheets and glaciers, with maybe a penguin or two thrown in. Yet most Antarctic plants and animals live in the permanently ice-free areas that cover about 1% of the continent. Our <a href="http://dx.doi.org/10.1038/nature22996">new research</a> predicts that these areas could grow by a quarter during this century, with mixed prospects for the species that currently live there. </p>
<p>Besides everyone’s favourite Emperor and Adélie penguins, terrestrial Antarctic species also include beautiful mosses, lichens, two types of flowering plants, and a suite of hardy invertebrates such as nematodes, springtails, rotifers and tardigrades, many of which are found nowhere else on Earth. Tardigrades – tiny creatures sometimes nicknamed “waterbears” – are so tough they can <a href="http://www.smithsonianmag.com/science-nature/how-does-the-tiny-waterbear-survive-in-outer-space-30891298">survive in space</a>.</p>
<p>Antarctica’s ice-free areas are currently limited to a scattering of rocky outcrops along the coastline, or cliff faces, or the tops of mountain ranges. They form small patches of suitable habitat in a huge sea of ice, much like islands. </p>
<p>As a result, the plants and animals that live there are often isolated from each other. But as Antarctica’s climate warms, we expect ice-free areas to get bigger and eventually start joining up. This would create more habitat for native species, but also new opportunities for non-native species to spread. </p>
<p>Our study, <a href="http://dx.doi.org/10.1038/nature22996">published today in Nature</a>, forecasts that climate change will expand Antarctica’s ice-free areas over the course of this century. Under the most severe scenario that we modelled (which is also the one on which the globe is <a href="http://dx.doi.org/10.1038/nclimate1783">currently tracking</a>), more than 17,000 square km of new ice-free area could emerge across the continent by 2100. </p>
<p>This would increase the current total ice-free area by nearly a quarter. The majority of this new ice-free land will be on the Antarctic Peninsula, which could have three times as much ice-free area as it does today. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=630&fit=crop&dpr=1 600w, https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=630&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=630&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=791&fit=crop&dpr=1 754w, https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=791&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/175982/original/file-20170628-25848-f94spw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=791&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Projected Antarctic ice melt this century.</span>
<span class="attribution"><a class="source" href="http://www.add.scar.org">Lee et al. (2017) Nature</a></span>
</figcaption>
</figure>
<h2>Brave new world</h2>
<p>As the ice-free areas expand, the distances between them will decrease, giving plants and animals more opportunity to spread through the landscape. On the Antarctic Peninsula, which has <a href="http://dx.doi.org/10.1038/nature11391">already warmed more than anywhere else in Antarctica</a>, many of the ice-free patches will expand so much that they will start joining together.</p>
<p>Will this increase in habitat availability benefit the plants and animals that live there? It will definitely provide new opportunities for some native plants and animals to expand their range and colonise new areas. The warming climate may also give a boost to species that are currently hampered by the lack of warmth, nutrients and water. Some Antarctic mosses, for example, are <a href="http://www.abc.net.au/news/science/2017-05-19/rapid-greening-of-antarctic-peninsula-drive--by-climate-change/8534368">expected to grow faster as temperatures rise</a>, and Antarctica’s two flowering plant species are <a href="http://dx.doi.org/10.1098/rstb.2006.1949">already expanding southward</a>.</p>
<p>However, the potential benefits seem likely to be outweighed by the negatives. The joining-up of habitat patches could allow species that have been isolated for much of their evolutionary past to meet suddenly. If the newcomers to a particular area outcompete the native species, then it may lead to localised extinctions. Over the coming centuries this could lead to the loss of many plants and animals, and the homogenisation of Antarctica’s ecosystems.</p>
<h2>Antarctic aliens</h2>
<p>An even bigger concern is that Antarctica’s great thaw could provide new opportunities for species to invade. Antarctica’s best bulwark against non-native species is its harsh climate and extreme weather, to which native Antarctic species have spent many thousands of years adapting. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/175975/original/file-20170628-24741-or8udg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A native Frisea springtail.</span>
<span class="attribution"><span class="source">Melissa Houghton</span></span>
</figcaption>
</figure>
<p>We already know that <a href="http://dx.doi.org/10.1007/s00300-014-1599-2">many plants and invertebrates are reaching Antarctica</a>, most often in food or cargo shipments. As the climate warms, some of these non-native species may be able to establish themselves on the Antarctic Peninsula, and the increasing connectivity will allow them to easily move through the landscape. Many of these animals and plants may become invasive, competing with the native species for space and resources. </p>
<p>We don’t know how Antarctica’s species will cope with the increasing competition. But if the sub-Antarctic islands provide any indication, the outlook is depressing. Australia’s World Heritage-listed <a href="http://whc.unesco.org/en/list/629">Macquarie Island</a>, for example, was severely impacted by invasive cats, rats, rabbits and mice (although it has since been <a href="http://www.abc.net.au/news/2014-04-07/macquarie-island-declared-pest-free-after-eradication-program/5373336">declared free of these pests</a> after an intensive eradication effort).</p>
<p>Several non-native species have already come to Antarctica, including the invasive annual meadowgrass <em>Poa annua</em> (a common weed around the world), which has <a href="https://doi.org/10.1017/S0954102010000982">colonised newly ice-free areas</a> left behind by retreating glaciers. It is thought to outcompete Antarctica’s native plants, although we don’t yet know what the impact will be on animals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/175985/original/file-20170628-25857-t8o40.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Invasive meadowgrass on Macquarie Island.</span>
<span class="attribution"><span class="source">Laura Williams</span></span>
</figcaption>
</figure>
<p>Humans – both scientists and tourists – are <a href="http://dx.doi.org/10.1073/pnas.1119787109">key transporters of non-native species to the continent</a>, and tourist numbers continue to grow (<a href="https://iaato.org/tourism-statistics">almost 37,000 visited in the 2016-17 summer</a>). </p>
<p>Biosecurity is paramount for the ongoing protection of Antarctica. If bags, shoes, clothes and field equipment are not properly cleaned and inspected before arriving on the continent, then non-native seeds, microbes and insects could be transported to Antarctica and begin to spread. </p>
<p>We call for protection of ice-free areas that will remain intact in a changing climate, and for the Antarctic scientific and tourism communities to pinpoint key areas where greater biosecurity and monitoring for invasive species may be needed.</p><img src="https://counter.theconversation.com/content/80140/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jasmine Lee is also affiliated with CSIRO. She receives funding from from the Holsworth Wildlife Research Endowment - Equity Trustees Charitable Foundation, the Ecological Society of Australia, and the Australian Antarctic Science Program (Project 4297).</span></em></p><p class="fine-print"><em><span>Justine Shaw receives funding from Australian Government’s National Environmental Science Programme through the Threatened Species Recovery Hub</span></em></p><p class="fine-print"><em><span>Richard Fuller receives funding from the Australian Research Council. </span></em></p>Climate change is set to expand Antarctica’s ice-free area, potentially helping native species to flourish but also paving the way for invasive species to gain a foothold.Jasmine Lee, PhD candidate, biodiversity conservation and climate change, The University of QueenslandJustine Shaw, Conservation Biologist, The University of QueenslandRichard Fuller, Associate Professor in Biodiversity and Conservation, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/761082017-04-13T13:58:16Z2017-04-13T13:58:16ZHeat from the Atlantic Ocean is melting Arctic sea ice further eastwards than ever before<figure><img src="https://images.theconversation.com/files/165121/original/image-20170412-25870-sfsu6n.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sea ice in the Arctic.</span> <span class="attribution"><span class="source">Tom Rippeth</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The seasonal sea-ice retreat across the Arctic Ocean is perhaps one of the most conspicuous indicators of climate change. In September 2012, a <a href="http://nsidc.org/arcticseaicenews/">new record was set</a> for the time that we have been tracking sea ice with satellites: the minimum sea ice extent was some 50% below the climatic average for that month. Four years on, and the <a href="http://nsidc.org/arcticseaicenews/">September 2016 record</a> tied with 2007 for the second lowest sea ice extent since measurements began in 1978.</p>
<p>The seasonal retreat of sea ice is largely because the atmosphere in the Arctic is heated under 24 hours of daylight in the summer, and this makes the ice melt. In the cold of the perpetual darkness of winter, the sea ice extent returns to its winter norm: the only heat available to slow sea ice growth is from winds and ocean currents moving warm air and water in from the south. </p>
<p>However, during the winter of 2016/17 the sea ice did not return to its winter norm. In fact, the sea ice extent was the <a href="http://nsidc.org/arcticseaicenews/">lowest ever recorded</a> for this time of year.</p>
<p>Though the Arctic is not exactly in the UK’s backyard, the changes in sea ice coverage are thought to be at least partly responsible for the recent <a href="http://www.nature.com/ngeo/journal/v7/n9/full/ngeo2234.html">run of severe weather events</a> experienced across the northern hemisphere. These include <a href="http://www.nature.com/ngeo/journal/v7/n12/abs/ngeo2277.html">unusually cold winter weather</a> across parts of Europe and the US, and <a href="http://advances.sciencemag.org/content/3/3/e1602751.full">deadly smogs</a> in parts of China.</p>
<p>The Arctic is warming about <a href="http://arctic.noaa.gov/Report-Card/Report-Card-2016">twice as fast</a> as the rest of the world. As the difference between atmospheric temperatures in the Arctic and mid-latitudes (<a href="https://www.spaceweatherlive.com/en/help/the-low-middle-and-high-latitude">which includes</a> the UK, part of North America, and a band of northern Europe and Asia) decreases, the speed at which weather systems (depressions) track across the Atlantic to northwestern Europe is reduced. This means that snow and rain can persist for longer, and high pressure systems are “harder to shift”, which can lead to further reductions in air quality.</p>
<h2>Warming warning</h2>
<p>The largest oceanic heat input to the Arctic comes from water that has been in the Atlantic Ocean, and has travelled through the Fram Strait and around Svalbard. This “Atlantic water” circulates around the Arctic in an anti-clockwise direction. This water is currently the <a href="http://instaar.colorado.edu/%7Emarchitt/reprints/spielhagenscience11.pdf">warmest it has been for 2,000 years</a> and now contains enough heat to completely melt the sea ice within a couple of years. </p>
<p>However, while this water is warmer than the ambient Arctic water, it is also saltier, and so heavier, too. It sits at depths of 100 to 400 metres across much of the Arctic Ocean. This means that the Atlantic water heat is insulated from the surface by a layer of lighter, colder and fresher Arctic Ocean water which sits above it.</p>
<p>Atlantic water contact with the sea surface – which then melts the sea ice impacting coverage and thickness – has <a href="http://www.nature.com/ngeo/journal/v8/n3/abs/ngeo2350.htmlhttp://www.nature.com/ngeo/journal/v8/n3/abs/ngeo2350.html">previously been restricted</a> to the region around Svalbard, where the Atlantic water enters the Arctic Ocean. However, new measurements reported by a team of international scientists have shown, for the first time, that previously insulated Atlantic water heat is now being <a href="http://science.sciencemag.org/content/early/2017/04/05/science.aai8204">stirred up to the sea surface</a>. This results in enhanced sea ice melt, much further to the east, north of Siberia. </p>
<p>We previously measured the upward Atlantic water heat flux in this region <a href="http://onlinelibrary.wiley.com/doi/10.1029/2008GL036792/">in 2007 and 2008</a>. At the time it was very modest. However, the new measurements estimate this flux to have increased by two to four times over the winters of 2013/14 and 2014/15. The result of this increase is that sea ice thickness has been reduced by between 18 and 40cm. This exceeds the impact of the atmospheric heat on sea ice melt alone (estimated to be 18cm). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=520&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=520&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165260/original/image-20170413-25901-lmhenr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=520&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A polar bear walks on the ice floes north of Svalbard.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/polar-bear-walking-across-vast-expanse-428511568?src=cTGuD0yuLx83f8SBBYu5HQ-1-3">wildestanimal/Shutterstock</a></span>
</figcaption>
</figure>
<p>The researchers attribute the change to a reduction in the vertical density gradient within the overlying Arctic water layer. The Atlantic water has moved closer to the sea surface, and created conditions much more like those found around Svalbard, where there is less sea ice. Lead researcher Igor Polyakov describes the change as the “atlantificiation” of this part of the Arctic Ocean.</p>
<p>These important new results highlight the increasing role of heat coming from the Atlantic Ocean in driving sea ice retreat in the Arctic Ocean. They are a profound sign of the planet’s changing climate, and show that there is a link between retreating Arctic sea ice and the severe weather that has been witnessed in mid-latitude countries.</p>
<p>Furthermore, they show that the impact of Atlantic water heat on sea ice is highly variable across the Arctic Ocean, with significant heat fluxes restricted to geographic “<a href="https://theconversation.com/potential-hot-spots-for-sea-ice-melting-identified-in-the-arctic-ocean-66233">hot spots</a>”. The identification of these hot spots will be key to improving how we forecast the weather in the northern hemisphere and understand how the retreat of Arctic sea ice impacts on it.</p><img src="https://counter.theconversation.com/content/76108/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tom Rippeth receives funding from the Natural Environmental Research Council and Bangor University. He is affiliated with the Liberal Democrats. </span></em></p>The link between melting sea ice and extreme weather has been known for a while, but now it’s happening further afield.Tom Rippeth, Professor of Physical Oceanography, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/595892016-05-18T19:45:47Z2016-05-18T19:45:47ZAntarctic glacier’s unstable past reveals danger of future melting<figure><img src="https://images.theconversation.com/files/122977/original/image-20160518-13478-18k74l5.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some parts of Antarctica's Totten Glacier are more stable than others.</span> <span class="attribution"><span class="source">UWA/ICECAP</span>, <span class="license">Author provided</span></span></figcaption></figure><p>New mapping of one of the most remote areas in Antarctica has revealed regions deep within Earth’s largest ice sheet that are particularly prone to rapid melting. </p>
<p>Our study, <a href="http://nature.com/articles/doi:10.1038/nature17447">published today in Nature</a>, is focused on East Antarctica’s Totten Glacier, the outlet for the world’s largest ice catchment. The results suggest that if rising global temperatures trigger the glacier to retreat rapidly – as has happened previously in its history – this region alone could deliver sea-level rises of well over a metre over the ensuing centuries. </p>
<p>The Totten Glacier region is a key area for understanding the long-term vulnerability of the Antarctic Ice Sheet, but until now, knowledge of this region’s glacial history has been very limited.</p>
<p>Our study shows that, although the region near the coast is quite stable on timescales of several millennia, regions further inland have potential for significant and rapid retreat as the climate warms.</p>
<p>Specifically, we identified two stable zones where the ice sheet is not prone to rapid collapse, and two unstable zones, where it is. We have also discovered that transitions between these states have happened repeatedly during the life of the ice sheet. </p>
<h2>Stable and not so stable</h2>
<p>As part of the international <a href="http://www.geos.ed.ac.uk/homes/awright4/icecap.html">ICECAP</a> project, my colleagues and I used ice-penetrating radar, as well as magnetic and gravity data, to chart the rocks beneath the glacier.</p>
<p>By mapping the shape of the ice-sheet and its base, as well as the thickness of the rocks and sediments beneath, we were able to study the characteristic patterns of erosion left behind by the ice sheet’s previous advances and retreats – thus revealing the ice sheet’s past behaviour.</p>
<p>The observed patterns suggest that the ice sheet has spent much of its history in one of two configurations: either the edge has been close to the current Antarctic coast (within 150 kilometres); or it has been located some 350-550 kilometres inland. In either of these states, the ice would be relatively stable, with this glacier providing sea level fluctuations of less than a metre over the course of glacial cycles.</p>
<p>But the pattern of erosion also shows that melting has periodically forced the ice sheet out of either of these stable states, causing the ice sheet to collapse and retreat far inland. These events might have typically driven up global sea levels by 1.3-1.4 metres over the course of a few centuries.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=438&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=438&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=438&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122969/original/image-20160518-13478-1oz5kal.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Main image: present-day configuration of the Antarctic ice sheet surface and its base. The ice sheet surface is shaded according to surface velocity, with glaciers in red. Blue-cyan tones indicate where the ice-sheet base (or the sea floor) is below sea level, yellow-brown tones indicates where the ice sheet base is above sea level. Inset diagrams show reconstructions of the ice sheet and the coast following retreat driven by climates warmer than today’s. All images are vertically exaggerated.</span>
<span class="attribution"><span class="source">ICECAP Collaboration</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>What is happening today?</h2>
<p>Previous studies from satellite data have indicated that the coastal part of the Totten Glacier region and its floating ice shelf are melting rapidly. Last year, the ICECAP team discovered that there is <a href="https://theconversation.com/melting-moments-a-look-under-east-antarcticas-biggest-glacier-40960">currently warm water circulating underneath a floating portion of the glacier</a> that is causing more melting than might have been expected. </p>
<p>Our results show that following a rapid loss of coastal ice due to the collapse of the floating ice shelf, this region is likely to respond more slowly than other parts of Antarctica to warming temperatures, due to the existence of a “stable zone”. </p>
<p>But as temperatures continue to increase, this glacier is likely to retreat into the unstable zone, and make a rapid and proportionally greater contribution to sea levels. </p>
<p>Our ice sheet modelling suggests that while the Totten region is not the first region in Antarctica to respond to warming climate, it is likely to become progressively more unstable as warming proceeds over hundreds to thousands of years. Ultimately this region could become the “fat end of the wedge” in terms of Antarctica’s overall contribution to rising seas, accounting for almost 15% of Antarctica’s total contribution to sea-level rise. This is likely to happen while other regions have become ice-free, or are stabilising after periods of rapid ice loss. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=285&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=285&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=285&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=358&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=358&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122970/original/image-20160518-13471-blp7gv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=358&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Impact of the Totten Glacier’s retreat on the Antarctic’s overall contribution to sea-level rise. The unstable retreat events in the Totten Glacier region cause significant upwards deviations of the overall Antarctic trend.</span>
<span class="attribution"><span class="source">SOURCE</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our results suggest that the Totten region has severe implications for global sea level rise in warming climate conditions, especially once warming reaches the critical thresholds likely to tip the glacier out of its stable states. Given the long timescales involved for ice-sheet melting it is difficult to say with confidence when this tipping point might be reached.</p>
<p>Increases to carbon dioxide levels today will commit us to temperature increases that persist for thousands of years. The upper limit of the coastal stable zone could be crossed under conditions similar to those predicted for the next century, based on the higher emissions scenarios envisaged by the Intergovernmental Panel on Climate Change.</p><img src="https://counter.theconversation.com/content/59589/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Aitken receives research funding from the Australian Research Council, the Science and Industry Endowment Fund and the State Government of Western Australia. These funding sources relate to other projects.
His contribution to this work was funded by the University of Western Australia's Goodeve Foundation.</span></em></p>New mapping shows how Antarctica’s huge Totten Glacier has retreated far inland, raising sea levels by more than a metre. Rising temperatures could trigger it to do so again.Alan Aitken, Assistant Professor, School of Earth and Environment, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/392532015-05-11T20:07:08Z2015-05-11T20:07:08ZSea level is rising fast – and it seems to be speeding up<figure><img src="https://images.theconversation.com/files/78570/original/image-20150420-25701-d3ufl1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C668%2C376&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rising sea levels are one of the clearest and most widespread manifestations of climate change.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/48346846@N08/15809431817/">Steven Godfrey</a></span></figcaption></figure><p><a href="http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter13_FINAL.pdf">Many observations</a> have shown that sea level rose steadily over the 20th century – and at a faster rate than over the previous centuries. It is also clear from both satellite and coastal observations that seas have risen faster over the past two decades than they did for the bulk of the 20th century.</p>
<p>More recently, <a href="http://imbie.org/imbie-2012/results/">several studies</a> have shown that the flow of ice and water into the oceans from Greenland and West Antarctica has increased since 1993. This raises an interesting question: has the rate of sea-level rise changed since 1993, when satellite observations began to give us a more complete picture of the global oceans?</p>
<p>Our <a href="http://dx.doi.org/10.1038/nclimate2635">new research</a> tackles this question by comparing satellite observations of sea level with those measured at the coast by tide gauges. We use this comparison to determine small biases in the satellite data that have changed over time. Understanding how the land supporting the tide gauges is moving becomes an important part of these comparisons. We found three important results.</p>
<p>First, the seas really have risen faster since 1993, relative to the slower rate over previous decades as evident in the tide gauge data. </p>
<p>Second, comparison of the coastal and satellite measurements reveal small differences in the early part of the satellite record from 1993 to 1999. After allowing for land motion at the tide gauges, the first six years of the satellite record marginally overestimates the sea-level trend. Our revised estimate of global mean sea-level rise for the satellite era (1993 to mid-2014) is about 2.6-2.9 mm per year (the exact value depends on how we estimate land motion) – slightly less than the <a href="http://www.tandfonline.com/doi/full/10.1080/01490419.2012.717862#abstract">previous estimate</a> of 3.2 mm per year. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/78534/original/image-20150419-3261-h05pws.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Satellite altimeters measure sea level by measuring the time it takes a radar pulse to make a round-trip from the satellite to the sea surface and back.</span>
<span class="attribution"><span class="source">NOAA/STAR</span></span>
</figcaption>
</figure>
<p>Third, previous estimates of the rate of rise from satellite data that didn’t incorporate the careful comparison with coastal sea-level measurements, as we have done in our recent study, showed a slower rate of rise over the past decade relative to the one before. Our revised record is clearly different and suggests that the rate of rise has increased, consistent with other observations of the increased contributions of water and ice from Greenland and West Antarctica. </p>
<p>However, sea level varies from year to year, as water is exchanged between the land and oceans (for example during the Australian floods associated with the 2010-11 and 2011-12 La Niña events), and as a result the observed increase in the rate of rise over the short satellite record is not yet statistically significant.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/78552/original/image-20150420-3249-fz0qdv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ice sheets covering West Antarctica and Greenland (pictured here south of Illulisat) are providing accelerating contributions to sea level.</span>
<span class="attribution"><span class="source">Ian Joughin</span></span>
</figcaption>
</figure>
<p>Strikingly, our estimate of the increase in the rate of rise is consistent with the <a href="http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter13_FINAL.pdf">projections of future sea level</a> published by the Intergovernmental Panel on Climate Change (IPCC). Currently, these projections forecast a rise of up to 98 cm by 2100 if greenhouse gas emissions are allowed to continue unabated (and even more if parts of the <a href="https://theconversation.com/shrinking-of-antarctic-ice-shelves-is-accelerating-39273">Antarctic ice sheet</a> collapse). If the world makes strong cuts to greenhouse gas emissions, the rise by 2100 is projected to be significantly less, somewhere between 28 cm and 61 cm. </p>
<h2>Coping with the impacts</h2>
<p>The increasing rate of sea-level rise is not good news for our coastal population, nor for the natural and built environment in the coastal zone. The world is currently not on track to achieve the lower range of projected sea-level rise. And of course, sea-level rise will not stop in 2100 – as in the current century, the magnitude of future sea-level rise will be linked to our greenhouse gas emissions. </p>
<p>Increasing rates of sea-level rise will place increasing stress on the coastal margin. Extreme sea level events will become more frequent. Inundation and erosion will affect our infrastructure, affect ecosystems and, in some regions, displace populations. Adaption in the coastal zone will occur – this adaption can be either planned or forced upon us by the natural environment. Information on <a href="https://theconversation.com/15-years-from-now-our-impact-on-regional-sea-level-will-be-clear-31821">regional sea level changes and their projections</a> are needed to underpin adaptation and mitigation strategies. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/79741/original/image-20150429-23372-ds05ix.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Coastal erosion near Winda Woppa resulting from extreme sea levels along the NSW coast during the April 2015 storms.</span>
<span class="attribution"><span class="source">Rick Wraight</span></span>
</figcaption>
</figure>
<p>It is important that <a href="https://theconversation.com/scrapping-sea-level-protection-puts-australian-homes-at-risk-21271">agencies in Australia</a> and worldwide consider the impact of accelerating sea levels and provide communities with advice and planning directions that are commensurate with the magnitude of the problem. Failure to consider these issues will mean painful and <a href="http://www.climatecouncil.org.au/coastalflooding">costly impacts</a>, particularly during <a href="https://theconversation.com/losing-higher-ground-hurricanes-and-sea-level-rise-10414">extreme events</a>. </p>
<h2>Continued monitoring of sea level is essential</h2>
<p>Despite progress, our understanding of sea-level change is incomplete, particularly when it comes to <a href="http://www.smh.com.au/comment/shrinking-antarctic-has-us-skating-on-thin-ice-20150419-1mmvh4.html">forecasting contributions from the ice sheets</a>. Currently, observed sea-level rise is consistent with the most recent projections. Continuing to know where sea level is tracking relative to projections is important for planning and early warning of any rate of rise that differs from current projections is vital. </p>
<p>Australia relies on other countries for launching and maintaining <a href="http://sealevel.jpl.nasa.gov/missions/">satellite missions</a> such as those used in our study. We provide an important contribution to the long-term monitoring of altimeter data that spans several different missions and space agencies – this is why <a href="https://theconversation.com/securing-the-future-of-australias-research-infrastructure-38908">long-term government support</a> via Australia’s <a href="http://www.imos.org.au/">Integrated Marine Observing System</a> is so valued.</p><img src="https://counter.theconversation.com/content/39253/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christopher Watson receives funding from the Australian Research Council and the NCRIS Integrated Marine Observing System</span></em></p><p class="fine-print"><em><span>John Church receives funding from the Australian Government funded Australian Climate Change Research Program and the NCRIS Integrated Marine Observing System.</span></em></p><p class="fine-print"><em><span>Matt King receives funding from Australian Research Council.</span></em></p>Since 1993, satellites have been used as well as tidal gauges to monitor sea level. A new calibration of this satellite record now shows that the rise in sea level is gathering pace.Christopher Watson, Senior Lecturer, Surveying and Spatial Sciences, School of Land and Food, University of TasmaniaJohn Church, CSIRO Fellow, CSIROMatt King, Professor, Surveying & Spatial Sciences, School of Land and Food, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/346272014-11-24T17:04:54Z2014-11-24T17:04:54ZRobot submarine looks under Antarctic to find out why sea ice is getting thicker<figure><img src="https://images.theconversation.com/files/279516/original/file-20190614-158967-p62s00.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="source">megablaster / shutterstock</span></span></figcaption></figure><p>For several years now climatologists have puzzled over an apparent conundrum: why is Antarctic sea ice continuing to expand, albeit at the relatively slow rate of about one to two percent per decade, while Arctic sea ice has been declining rapidly (by some 13% per decade in late summer)?</p>
<p>Just a few weeks ago the Antarctic saw a <a href="http://nsidc.org/news/newsroom/arctic-sea-ice-continues-low-while-antarctic-reaches-new-record-high">third consecutive record</a> year of sea ice coverage. The two previous records were set in 2012 and 2013. </p>
<p>To help get to the bottom of this mystery, one team of scientists have enlisted an underwater robot to help measure the thickness of the ice. Their vehicle, known as SeaBED, has an upwards looking sonar which maps the underside of ice floes and provides novel, highly-detailed three-dimensional maps of Antarctic sea ice. The researchers present their findings in the journal <a href="http://dx.doi.org/10.1038/ngeo2299">Nature Geoscience</a>.</p>
<p>Measuring a total of ten ice floes covering more than 500,000 square metres, they found mean ice thicknesses of 1.4 to 5.5 metres. In some places the ice was up to 16 metres thick. This is much thicker than has been gauged by previous more limited field-based (mainly ship-based) measurements, possibly because ships tend to avoid the areas of thicker sea ice, so there may very well be a sampling selection bias. </p>
<p>Satellites would ideally be able to assess ice thickness over a much wider area. However, although they have had some success in the Arctic, at the other end of the world satellites are severely hampered by our poor knowledge of how much snow there is on top of any given area of Antarctic sea ice.</p>
<p>The researchers report that the ice they measured was in its first year of growth. This is important because it is the multi-year sea ice (ice that survives more than one summer melt season) which is more susceptible to thickness growth through deformation and ridging. </p>
<p>Previous estimates of mean thickness for first-year Antarctic sea-ice – which date back to at least 1986 – suggest it is no more than around a metre thick on average. It has long been recognised however that much thicker multi-year ice floes exist – especially near the coast and the Antarctic Peninsula, where sea-ice ridges can be the size of a house.</p>
<p>Although the new study is important, especially from an innovation/technological point of view, I would like to see this kind of analysis repeated across a range of different areas, and if possible seasons and years. At the end of winter around 20 million square kilometres of sea around the Antarctic is covered by ice – an area larger than Russia. The surveyed zone is tiny in comparison.</p>
<h2>Good news</h2>
<p>If the results are confirmed by future work, they suggest Antarctic sea-ice may be more resilient towards climate warming than has previously been appreciated. </p>
<p>Also, changes in the sea ice will in turn affect land-based glacial ice and free-floating ice-shelves if the sea-ice suddenly gets removed (or is thicker than realised). This is especially important in regions next to the strongly warming Antarctic Peninsula where some ice shelves have dramatically broken away into the ocean.</p>
<p>However, it will be some time yet before we know answers to the crucial question of what has caused recent sea-ice growth in Antarctica: is it changes in ocean currents, maybe related to an increase in fresher, colder sub-surface meltwaters running off from the great continental ice sheets?</p>
<p>Nevertheless thicker Antarctic sea-ice cover has profound implications. Ice thickness closely controls the exchange of energy between the ocean beneath and the air above – without ice cover, too much heat will leave the oceans and join the atmosphere.</p>
<p>Although ice is a very effective insulator, as soon as it reaches a few tens of centimetres thickness, equally important are holes in the ice cover. These holes, knows as leads and polynyas (leads are long rectilinear channels in the ice, while “polynya” comes from the Russian from “open” and is a larger, lake-like opening) act as natural vents or chimneys, releasing hundreds of watts of heat per square metre into the overlying atmosphere. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/65370/original/image-20141124-19612-25s5ko.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Polynyas near Pine Island Glacier, Antarctica.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/nasaearthobservatory/6358408909">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Any changes in the distribution of ice thickness can dramatically affect the points where these features form and their persistence. Thus it is fair to say that Antarctic sea ice thickness plays a pivotal role in what we call sea ice-climate feedbacks, where levels of ice cover are strongly linked to ongoing global climate change and vice versa.</p>
<p>It is therefore crucial for scientists modelling sea ice behaviour to have a good knowledge of thickness distribution to feed their models. This study represents a significant step forward.</p><img src="https://counter.theconversation.com/content/34627/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Edward Hanna does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>For several years now climatologists have puzzled over an apparent conundrum: why is Antarctic sea ice continuing to expand, albeit at the relatively slow rate of about one to two percent per decade, while…Edward Hanna, Professor of Climate Change, University of SheffieldLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/321712014-09-26T05:31:52Z2014-09-26T05:31:52ZWhy ice sheets will keep melting for centuries to come<p>Ice sheets respond slowly to changes in climate, because they are so massive that they themselves dominate the climate conditions over and around them. But once they start flowing faster towards the shore and melting into the ocean the process takes centuries to reverse. Ice sheets are nature’s freight trains: tough to start moving, even harder to stop.</p>
<p>We know this process has been going back and forth throughout history – it’s why we’ve had ice ages and warm periods. But until now we haven’t known exactly how quickly ice sheets retreated and reformed. New research published in the journal <a href="http://www.nature.com/ncomms/2014/140925/ncomms6076/full/ncomms6076.html">Nature Communications</a> gives us an answer, and it isn’t great news. </p>
<p>It turns out sea levels often rose at scary rates in response to natural climate changes, long before mankind began pumping carbon into the atmosphere.</p>
<p>In the short-term sea level is affected by ocean warming and so-called “<a href="http://www.ipcc.ch/ipccreports/tar/wg1/411.htm">thermal expansion</a>”, or melting glaciers based on land. These changes can occur quickly – within a decade – but their impact on sea level is relatively small, in the tens of centimetres. The drivers of longer-term sea level rise, over decades or centuries, are the continental ice sheets of Greenland and Antarctica. </p>
<p>On the fringes of these ice sheets are “ice shelves” stretching far out into the ocean. Ice shelves can be hundreds of meters thick and, because 90% of ice in water floats below the surface, they remain “grounded” on the sea floor as long as the sea is less deep than 90% of the ice shelf thickness. Where the sea floor is deeper or the ice shelf gets thinner, there will be an area of floating land ice; here, warming ocean water can get underneath and melt the ice. Once sufficiently destabilised, an ice shelf can break up catastrophically. </p>
<figure> <img src="http://www.jpl.nasa.gov/images/earth/antarctica/20140512/glacier-640.gif"><figcaption>One small portion of the West Antarctic ice shelf slides into the sea. Images via NASA</figcaption></figure>
<p>Such an ice shelf collapse takes the brakes off the ice stream that feeds into the ice shelf, and land ice starts to flow much quicker towards the ocean. </p>
<p>Ice flow is a relatively slow process, and it takes some forcing to get a major ice sheet to systematically respond (like trying to set a fully loaded freight train into motion). Once moving, however, it will be equally hard to arrest that movement (like trying to stop a moving, fully loaded freight train). </p>
<p>Still, we cannot ignore it, because the sheer volume of land ice on Earth is enormous – equivalent to more than <a href="http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch4s4-1.html">65m of global sea level rise</a>; Greenland alone accounts for 6 to 7m, West Antarctica for some 5-6m, and East Antarctica for the remainder. These melting ice sheets will dominate major sea level changes for centuries to come. </p>
<p>We can learn something about what to expect by examining sea level changes during the past five ice-age cycles (past half million years), especially through comparing them with the total amount of ice on the planet at the time.</p>
<p>During a peak ice age, Earth held almost three times as much land ice as it holds today. For instance, during the most recent ice age the ice sheet over North America was 10-20% larger than the one we see today over all of Antarctica.</p>
<p>During warm periods in between ice ages the sea was often close to its present level but occasionally reached up to 8 or 9m above today’s shoreline – the equivalent of melting 1.3 Greenlands today.</p>
<h2>Diving into deep-sea data</h2>
<p>To get a sense of how quickly the sea went up and down, we need highly detailed and well-dated records. Over the past decade I’ve led a team of scientists at the University of Southampton and the Australian National University who have developed such records using data from the Red Sea.</p>
<p>The Red Sea has a very shallow and narrow connection with the open Indian Ocean. It also evaporates quickly – the equivalent of 2m of water each year – so new water must constantly flow in to top up sea levels and to avoid it getting too salty. </p>
<p>But such inflow is restricted by the tiny gap between Djibouti and Yemen, and in the past that connection was even smaller. As a result, the Red Sea was much saltier during previous ice ages, when sea level stood more than 100m below the present. Using microfossils from drill cores from the sea floor we can measure salinity through time and translate this to sea level changes in the Red Sea connection with the Indian Ocean. We were able to assess timings more accurately by comparing these sea level records to climate records from caves, which can be precisely dated by looking at radioactive decay in uranium.</p>
<p>So now we had a detailed sea level record, with a well-defined timescale. Finally, we could work out rates of past sea level changes, and compare changing sea levels with well-dated reconstructions of temperature and CO<sub>2</sub> changes (from ice cores).</p>
<p>This allowed us to assess the speed of some 120 sea level rises in the past. Previously, this was possible only for one recent event. Now, for the first time, we had the information to look at how sea levels responded to natural climate change.</p>
<p>It appears the sea level could rise as quickly as 5.5m per century. However this only happened at the abrupt endings of ice ages, starting with about three times the modern ice volume. When starting with double the modern ice volume or less, sea levels did not rise faster than 2m per century. When global ice volume was similar to the present, the sea typically rose less than 1 to 1.5m per century. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/60061/original/z7z2qnjm-1411655886.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A one metre rise in sea level would flood the areas shaded red.</span>
<span class="attribution"><a class="source" href="http://www.nasa.gov/topics/earth/tipping_points_hiresmulti_prt.htm">NASA</a></span>
</figcaption>
</figure>
<p>So it seems the fastest losses of ice occur when there is more ice. Not much of a surprise, perhaps, but now at least we have some real numbers to say how fast, and how much ice. And the speed the sea can rise during periods with modern ice volumes is still worrying – a <a href="http://www.telegraph.co.uk/earth/environment/climatechange/9706587/Doha-Sea-levels-to-rise-by-more-than-1m-by-2100.html">1m rise this century</a> would hugely affect millions of people. Given that Earth has achieved these rates even when warming was much slower than today, such a rise is very possible.</p>
<h2>How long will it take?</h2>
<p>In the 120 different events we looked at, ice sheets went from initial change to maximum retreat within 400 years 68% of the time, and within 1100 years for 95%. In other words: once triggered, ice sheet reduction (and therefore sea level rise) kept accelerating relentlessly for many centuries. </p>
<p><a href="http://www.highstand.org/erohling/Rohling-papers/2013-Rohling-ea-Sci-Repts-srep03461.pdf">Research</a> we carried out previously found that modern sea level rise seems to be conforming to what we would expect from (high end) natural responses to warming. That is: after 150 years of increasing (man made) warming, the ice sheets would only recently be reaching the point where they start making a noticeable contribution to sea level rise. </p>
<p>But that time has come and, once ice sheets start to melt, the freight train is in motion. It will then keep moving for many centuries to come, no matter how hard we stamp on the brakes.</p><img src="https://counter.theconversation.com/content/32171/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eelco Rohling receives funding from the UK Natural Environment Research Council, and from the Australian Research Council.</span></em></p>Ice sheets respond slowly to changes in climate, because they are so massive that they themselves dominate the climate conditions over and around them. But once they start flowing faster towards the shore…Eelco Rohling, Professor of Ocean and Climate Change, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/269572014-05-20T04:06:48Z2014-05-20T04:06:48ZWe can now only watch as West Antarctica’s ice sheets collapse<figure><img src="https://images.theconversation.com/files/48936/original/ztztfyt8-1400551967.jpg?ixlib=rb-1.1.0&rect=16%2C16%2C3369%2C2009&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Thwaites Glacier is among several in West Antarctica that is already retreating.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>Antarctic climate science is having a moment – a worrying moment. Three new studies have all concluded that the West Antarctic Ice Sheet has begun to collapse. This collapse will impact humanity for generations to come, and the indications are that it is too late to stop it.</p>
<p>Satellite measurements compiled by UK researchers have shown that Antarctica <a href="http://onlinelibrary.wiley.com/doi/10.1002/2014GL060111/abstract">is losing 160 billion tonnes of ice per year</a>, mainly through thinning of West Antarctica’s ice sheets.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=513&fit=crop&dpr=1 600w, https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=513&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=513&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=645&fit=crop&dpr=1 754w, https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=645&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/48939/original/v8j9kx85-1400553204.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=645&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rates of ice loss across Antarctica.</span>
<span class="attribution"><a class="source" href="http://www.esa.int/spaceinimages/Images/2014/05/Antarctica_s_ice_loss">ESA</a></span>
</figcaption>
</figure>
<p>Meanwhile, a NASA-linked study has found that <a href="http://onlinelibrary.wiley.com/doi/10.1002/2014GL060140/abstract">major West Antarctic glaciers have retreated by several kilometres over the past two decades</a>, and researchers at the University of Washington found that one of these, the Thwaites Glacier, is <a href="http://www.sciencemag.org/content/344/6185/735.abstract">set to collapse over the coming centuries</a>, potentially triggering 3 metres of sea level rise.</p>
<p>The potential collapse of West Antarctica’s ice sheets is not just a problem for Antarctica. It will dramatically change coastlines all over the world.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/48937/original/jds633xx-1400552366.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">West Antarctica’s unstable glaciers.</span>
<span class="attribution"><a class="source" href="http://www.nasa.gov/jpl/news/antarctic-ice-sheet-20140512/#.U3q7hFiSyY_">NASA</a></span>
</figcaption>
</figure>
<h2>The ‘climate gorilla’</h2>
<p>Several years ago, at a science forum in Canberra, we were encouraged to imagine a “greenhouse future”. I identified the West Antarctic Ice Sheet as the 800-pound gorilla hiding in the climate closet. Why? The ends of many of the glaciers that drain this ice sheet are already significantly below sea level, and the ice sheet is not hemmed in by mountains, as Greenland’s ice sheets are. </p>
<p>The combination of rising sea level and the warming Southern Ocean will release the ice sheet from its grounding line – the NASA study has already found that the glaciers’ grounding lines are in rapid retreat. Without an anchor on land, the ice sheets’ collapse is inevitable and cannot be slowed. </p>
<p>The total collapse of the vulnerable parts of West Antarctica’s ice sheets would raise sea levels by at least 3 metres. The possibility of this happening has now moved from the hypothetical to an unfortunate reality. The best we can now hope for is that this collapse will be slow and stately, and take centuries to unfold. </p>
<p>If this is the case, then civilizations can probably adapt to the havoc this will cause to coastal communities. However, we have <a href="http://www.sciencemag.org/content/337/6091/216.abstract">evidence from prehistoric warm periods that this could occur over decades</a>. At this point we don’t know long it will take, but we do know that the climate forcing today is much stronger than at any time in over 50 million years. </p>
<p>Given we have made so little progress on limiting our global carbon emissions, the odds are that ice-sheet collapse will only accelerate. Those of us who study climate history are confident that once this sort of collapse begins, it will not stop. </p>
<p>The celebrated US climatologist Wally Broecker often talks about the idea that we are playing Russian Roulette with the climate. In West Antarctica, we have just loaded another barrel. With apologies to Clint Eastwood, are we feeling lucky?</p>
<p>If not, then we are witnessing the beginning of the destruction of trillions of dollars’ worth of coastal infrastructure.</p>
<h2>Lighting the fuse</h2>
<p>You can be sure that the insurance industry is paying attention. How long will it be before property less than 5 metres above sea level is uninsurable? I hope it is a long time, but we will all be watching very closely how fast the West Antarctic Ice Sheet collapse accelerates. </p>
<p>The US glaciologist Richard Alley told the <a href="http://www.nytimes.com/2014/05/13/science/earth/collapse-of-parts-of-west-antarctica-ice-sheet-has-begun-scientists-say.html">New York Times</a> that “if we have indeed lit the fuse on West Antarctica, it’s very hard to imagine putting the fuse out”.</p>
<p>Another way of putting it is that we appear to have crossed a tipping point. As Alley also pointed out, there are many other fuses that could be lit, and probably will be, if the collapse markedly accelerates - and these would add to the rate and magnitude of the sea level rise. </p>
<p>One of those potential fuses is the <a href="http://www.nature.com/ncomms/2013/131205/ncomms3857/full/ncomms3857.html">Totten Glacier</a>, on the margin of the East Antarctic Ice Sheet. In this area, a rift in the Antarctic crust allows sea water to extend hundreds of kilometres under the ice, literally undermining the ice. </p>
<p>I am involved with a joint Australian-American <a href="https://sites.google.com/site/tottenexpedition">project</a> that will <a href="http://www.climatefutures.mq.edu.au/keops2-mission">investigate</a> this area’s past and future vulnerability to rising seas and warmer waters. </p>
<p>While we scramble to work out what is happening to the frozen continent, the signs are that it is changing before our eyes, and changing rapidly.</p><img src="https://counter.theconversation.com/content/26957/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bradley Opdyke receives funding from the ARC and the International ocean Drilling Program.</span></em></p>Antarctic climate science is having a moment – a worrying moment. Three new studies have all concluded that the West Antarctic Ice Sheet has begun to collapse. This collapse will impact humanity for generations…Bradley Opdyke, Researcher, ANU College of Physical and Mathematical Sciences, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/198072013-11-11T01:06:00Z2013-11-11T01:06:00ZMelting ice leaves polar ecosystems out in the sun<figure><img src="https://images.theconversation.com/files/34328/original/bckdqvbn-1383534809.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The dark waters under Antarctic ice are home to many unique species. </span> <span class="attribution"><span class="source">Graeme Clark</span></span></figcaption></figure><p>It is no secret that climate change is transforming the polar regions. Retreating glaciers, melting ice-caps and changing sea ice patterns are frequently reported in both the Arctic and Antarctic, and with these come dramatic changes to polar ecosystems.</p>
<p>But new research <a href="http://onlinelibrary.wiley.com/doi/10.1111/gcb.12337/abstract">published this week</a> in <em>Global Change Biology</em> reveals that polar ecosystems may be even more sensitive to climate change than previously thought. This is the result of a peculiar interaction between two environmental variables that only occurs at high latitudes.</p>
<h2>Change in light with early ice-loss</h2>
<p>Polar ecosystems are typically covered by snow and ice during winter, so receive almost all their annual light during summer when they’re ice-free. Warming temperatures and changing wind patterns mean that in many polar regions the summer ice-free period is expanding, with the ice melt occurring earlier in summer, and freeze occurring later.</p>
<p>This increases the amount of light reaching polar ecosystems per year, but it’s not a gradual increase. The tilt of the Earth means that summer days get far more light than winter, and in many places early ice melt will bring the ice-free period closer to the summer solstice (when the amount of sunlight reaches maximum). So as the ice melts earlier, the amount of sunlight reaching some ecosystems per year will increase exponentially. </p>
<h2>Ecological tipping points</h2>
<p>Events where small changes in environmental conditions — such as early ice melt — cause rapid and extensive ecological change are known as “tipping points”. Small changes in the timing of sea ice melt will produce large changes in annual light, which in turn will have major consequences for polar ecosystems.</p>
<p>Light is important because it controls a fundamental aspect of ecosystems: what type of organisms are the most abundant. From this perspective there are two main types of organisms: those, such as plants, that make their own food from sunlight (phototrophs), and those, mostly animals, that do not need sunlight and have to eat other organisms (heterotrophs). </p>
<p>Because some polar ecosystems receive only small amounts of sunlight, they are dominated by animals, as they generally do not need light to survive. But this could easily change if light increases due to melting ice. Many polar ecosystems could shift to having fewer animals and become dominated by plants and algae. </p>
<h2>Vulnerable marine life</h2>
<p>Our study looks at this effect on the Antarctic sea floor. We found that even a slight shift in the date of the annual sea ice melt can cause a tipping point where unique, invertebrate communities used to living in the dark are replaced by algae. </p>
<p>Near-shore areas of sea floor in both polar regions are vulnerable to this process, which could profoundly reduce coastal biodiversity. We predict that in areas where sea ice departs earlier in summer, biodiversity on the seabed could be reduced by as much as one-third within decades.</p>
<p>Invertebrates in the communities at risk include <a href="http://en.wikipedia.org/wiki/Sponge">sponges</a>, <a href="http://en.wikipedia.org/wiki/Bryozoa">bryozoans</a>, <a href="http://en.wikipedia.org/wiki/Tunicate">sea squirts</a> and worms. These animals perform important functions such as filtering of water and recycling of nutrients, and are also food for fish and other creatures.</p>
<h2>Where and when?</h2>
<p>Sea ice is not changing uniformly across space. It is <a href="https://theconversation.com/why-is-antarctic-sea-ice-growing-19605">actually growing</a> in some parts of Antarctica. </p>
<p>In other areas, it is diminishing fast. The West Antarctic Peninsula has seen a lengthening of the ice-free period by five days per year for the past 30 years, and sea ice extent in the Arctic is in sharp decline.</p>
<p>Our modelling shows that recent changes in ice and snow cover at the poles have already transformed the amount of light reaching large areas of the Arctic and Antarctic annually. The areas most vulnerable to future change in light are the ones that lose their ice in the months immediately following the summer solstice.</p>
<h2>Effects on other ecosystems</h2>
<p>This light-driven tipping point can be applied to lots of other ecosystems that are seasonally covered by snow or ice. These include high latitude land, lake, and shallow marine ecosystems. It’s likely that an expansion of Arctic vegetation and marine algae is driven by this process. </p>
<p>Changes won’t stop at plants - anything that eats or uses plants for habitat may also be affected. Increasing amounts of seaweed at the poles could support more fish and invertebrate grazers, and changes in plankton abundance might affect whales and krill.</p>
<p>The complexity of ecosystems makes it difficult to predict the full range of repercussions. But it’s clear that the poles are going to see some dramatic changes in coming decades.</p><img src="https://counter.theconversation.com/content/19807/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emma Johnston receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Jonathan Stark receives funding from the Australian Antarctic Division.</span></em></p><p class="fine-print"><em><span>Martin Riddle receives funding from the Australian Antarctic Science Program.</span></em></p><p class="fine-print"><em><span>Graeme Clark and John Runcie do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It is no secret that climate change is transforming the polar regions. Retreating glaciers, melting ice-caps and changing sea ice patterns are frequently reported in both the Arctic and Antarctic, and…Graeme Clark, Research Associate in Ecology, UNSW SydneyEmma Johnston, Associate Professor of Marine Ecology and Ecotoxicology, UNSW SydneyJohn Runcie, Honorary Research Associate in Biological Sciences, University of SydneyJonathan Stark, Senior Research Scientist in Antarctic Marine Ecology, Australian Antarctic DivisionMartin Riddle, Program Leader, Terrestrial and Nearshore Ecosystems, Environmental Change and Conservation, Australian Antarctic DivisionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/197312013-10-31T13:09:03Z2013-10-31T13:09:03ZIf next summer is rained off, blame the melting Arctic<figure><img src="https://images.theconversation.com/files/34179/original/wfpy9j2s-1383221427.jpg?ixlib=rb-1.1.0&rect=0%2C228%2C1001%2C718&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Another great British summer.</span> <span class="attribution"><span class="source">[Duncan]</span></span></figcaption></figure><p>Most people saw the warm dry weather from June to September as a welcome, but freak, occurrence. Because, as anyone who invested in floaty dresses, barbecues or expensive sunglasses in previous years will know, recent summers in Britain and north-western Europe have been unusually wet.</p>
<p>From 2007 to 2012, sunshine has been lower and rainfall higher than average, with 2012 - the summer that never was - the wettest for more than a century. With rainfall 80% higher than average, there were frequent floods, substantial damage to property, deaths and serious consequences for farming and tourism.</p>
<p>At the same time, during these summers, the amount of Arctic sea ice was very low. The summers between 2007 and 2012 were the six lowest years on record, with 2012 an all-time low. Could melting sea ice and wet summers be related?</p>
<p>In my <a href="http://iopscience.iop.org/1748-9326/8/4/044015/article">recent study</a> I used a climate model to investigate what impact the loss of Arctic sea ice has on weather patterns over Europe. The amount of sea ice cover in the model was changed in a controlled manner while other factors known to influence European weather were held constant. This allowed me to isolate and measure the affects of melting sea ice.</p>
<p>The model confirmed that when sea ice cover shrunk, the UK and north-western Europe experienced wetter summers. The pattern of rainfall anomalies in the model looked very similar to those observed in recent years. It seems reasonable to conclude that the loss of Arctic sea ice is one contributing factor in these washed-out summers.</p>
<h2>Jet stream</h2>
<p>Another factor that strongly influences the quality of European summers is the position of the <a href="http://www.metoffice.gov.uk/learning/wind/what-is-the-jet-stream">jet stream</a>. Jet streams are currents of strong winds, around 10km up in the atmosphere. Generally these winds blow from west to east, carrying weather systems and rain with them. During the summer, the jet stream normally lies between Scotland and Iceland, so heavy weather is carried through the Atlantic north of the British Isles. But when the jet stream shifts south, as it did for prolonged periods during the summers between 2007 and 2012, that unseasonable wet weather makes landfall in the UK.</p>
<p>The model confirmed that melting sea ice causes the jet stream to shift further south than normal, increasing the frequency of cloudy, cool and wet summers over north-western Europe. In contrast, Mediterranean Europe experienced drier conditions as sea ice was reduced.</p>
<h2>The bigger picture</h2>
<p>However, missing sea ice is only partially to blame for these soggy summers. A <a href="http://www.nature.com/ngeo/journal/v5/n11/full/ngeo1595.html">previous study</a> showed how European rainfall is influenced by a slow natural cycle of warming and cooling in the uppermost levels of the North Atlantic. Since the late 1990s, the Atlantic has been in the warm phase of that cycle - known as the <a href="http://www.cgd.ucar.edu/cas/catalog/climind/AMO.html">Atlantic Multidecadal Oscillation</a> - which is thought to bring with it greater risk of wet summers. So the combination in recent years of low Arctic sea ice and a warmer Atlantic have further increased the odds of wet summers. Together these two factors help explain our lack of sunshine and booming welly sales through the last few summers.</p>
<p>But there is one other factor that cannot be ignored: the natural, chaotic and completely unpredictable element of weather systems - not least in Britain, which has always had a more than average amount of unpredictable weather. Atmospheric variability can, and often does, exceed the influence of Arctic sea ice. Melting sea ice may increase the odds of a wet summer, but it will not lead to a wet summer every year. Buying extra lottery tickets increases your chances of winning, but clearly does not guarantee success.</p>
<p>This summer just gone is perhaps a timely reminder - despite warmer-than-average sea surface temperatures in the Atlantic and lower-than-average Arctic sea ice cover, summer 2013 turned out to be quite warm, dry and sunny. The Met Office reports that the UK’s 2013 summer was [the driest since 2003](http://www.metoffice.gov.uk/climate/uk/2012/summer.html](http://www.metoffice.gov.uk/climate/uk/2012/summer.htm).</p>
<h2>Future implications</h2>
<p>What does this all mean for future summers? Will there be opportunity to wear those dresses again before the moths get to them? The Atlantic Ocean will return to its cool phase in the next decade, which is expected to bring with it warmer and drier summers. But Arctic sea ice on the other hand is expected to <a href="http://www.theguardian.com/uk/2012/jul/18/wet-weather-boosts-cinemas-indoor">continue melting</a>, favouring potentially wetter summers. The outcome of this climate tug-of-war is uncertain and hard to predict - and in that respect, it’s business as usual for the British weather.</p><img src="https://counter.theconversation.com/content/19731/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Screen receives funding from the Natural Environment Research Council, UK.</span></em></p>Most people saw the warm dry weather from June to September as a welcome, but freak, occurrence. Because, as anyone who invested in floaty dresses, barbecues or expensive sunglasses in previous years will…James Screen, Research Fellow, Exeter Climate Systems Group, University of ExeterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/196052013-10-28T19:18:07Z2013-10-28T19:18:07ZWhy is Antarctic sea ice growing?<figure><img src="https://images.theconversation.com/files/33911/original/m9k29fk5-1382934278.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This winter there was more sea ice than ever in Antarctica. </span> <span class="attribution"><span class="source">Flickr/august allen</span></span></figcaption></figure><p>Recently NASA <a href="http://earthobservatory.nasa.gov/IOTD/view.php?id=82160">reported</a> that this year’s maximum wintertime extent of Antarctic sea ice was the largest on record, even greater than the previous year’s record.</p>
<p>This is understandably at odds with the public’s perception of how polar ice should respond to a warming climate, given the dramatic headlines of severe decline in Arctic summertime extent. But the “paradox of Antarctic sea ice” has been on climate scientists’ minds for some time.</p>
<h2>Continental v. sea ice</h2>
<p>First off, sea ice is different to the “continental ice” associated with polar ice caps, glaciers, ice shelves and icebergs. Continental ice is formed by the gradual deposition, build up and compaction of snow, resulting in ice that is hundreds to thousands of metres thick, storing and releasing freshwater that influences global sea-level over thousands of years.</p>
<p>Sea ice, though equally important to the climate system, is completely different. It is the thin layer (typically 1-2m) of ice that forms on the surface of the ocean when the latter is sufficiently cooled enough by the atmosphere. </p>
<p>From there sea ice can move with the winds and currents, continuing to grow both by freezing and through collisions (between the floes that make up the ice cover). When the atmosphere, and/or ocean is suitably warm again, such as in spring or if the sea ice has moved sufficiently towards the equator, then the sea ice melts again.</p>
<h2>Antarctic v. Arctic</h2>
<p>Secondly, we need to understand that the Arctic and Antarctic climate systems are very different, particularly in sea ice. </p>
<p>In the Arctic, sea ice forms in an ocean roughly centred on the North Pole that is surrounded by continents. A relatively large (though diminishing) proportion of the ice persists over multiple years before ultimately departing for warmer latitudes through exit points such as Fram Strait between Greenland and Svalbard. </p>
<p>In the south, on the other hand, sea ice forms outwards from the continental Antarctic Ice Sheet, where it is exposed to and strongly influenced by the winds and waters of the Southern Ocean. Here, there is a much stronger seasonal ebb and flow to sea ice coverage as over 80% of the sea ice area grows each autumn-winter and decays each spring-summer. This annual expansion-contraction from about 4 to 19 million square kms is one of the greatest seasonal changes on the Earth’s surface.</p>
<h2>Area v. volume</h2>
<p>Finally we need to remember that “extent” or “areal coverage” is only one way with which we monitor and study sea ice. </p>
<p>Sea ice turns out to be a very complex and variable medium that is very difficult to observe over large-scales. It is also constantly moving and restructuring. Until we achieve the “holy grail” of monitoring total sea ice volume from space and how it changes over time (and there are great steps towards this with European Space Agency’s environmental research satellite CryoSat-II), we are limited to interpreting its global behaviour through area.</p>
<h2>What happened this winter?</h2>
<p>This winter, the maximum total Antarctic sea ice extent was reported to be 19.47 million square kilometres, which is 3.6% above the winter average calculated from 1981 to 2010. This continues a trend that is weakly positive and remains in stark contrast to the decline in Arctic summer sea ice extent (2013 was 18% below the mean from 1981-2010). </p>
<p>To further complicate this picture, we find this net increase actually masks strong declines in particular regions around Antarctica, such as in the Bellingshausen Sea, which are on par or greater than those in the Arctic.</p>
<p>So while there is much greater attention given to the Arctic decline and the prediction of “ice-free summers” at the North Pole this century, Antarctic climate scientists still have their work cut out to understand the regional declines amidst the mild “net” expansion occurring in the southern hemisphere.</p>
<p>Here are some of the leading hypotheses currently being explored through a combination of satellite remote sensing, fieldwork in Antarctica and numerical model simulations – to help explain the increasing trend in overall Antarctic sea ice coverage:</p>
<ul>
<li><p>Increased westerly winds around the Southern Ocean, linked to changes in the large-scale atmospheric circulation related to ozone depletion, will see greater northward movement of sea ice, and hence extent, of Antarctic sea ice.</p></li>
<li><p>Increased precipitation, in the form of either rain or snow, will increase the density stratification between the upper and middle layers of the Southern Ocean. This might reduce the oceanic heat transfer from relatively warm waters at below the surface layer, and therefore enhancing conditions at the surface for sea ice.</p></li>
<li><p>Similarly, a freshening of the surface layers from this precipitation would also increase the local freezing point of sea ice formation.</p></li>
<li><p>Another potential source of cooling and freshening in the upper ocean around Antarctica is increased melting of Antarctic continental ice, through ocean/ice shelf interaction and iceberg decay.</p></li>
<li><p>The observed changes in sea ice extent could be influenced by a combination of all these factors and still fall within the bounds of natural variability.</p></li>
</ul>
<p>The take home messages is that while the increase in total Antarctic sea ice area is relatively minor compared to the Arctic, it masks the fact that some regions are in strong decline. Given the complex interactions of winds and currents driving patterns of sea ice variability and change in the Southern Ocean climate system, this is not unexpected. </p>
<p>But it is still fascinating to study.</p><img src="https://counter.theconversation.com/content/19605/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Guy Williams has received funding from the Australian Academy of Science. </span></em></p>Recently NASA reported that this year’s maximum wintertime extent of Antarctic sea ice was the largest on record, even greater than the previous year’s record. This is understandably at odds with the public’s…Guy Williams, Researcher, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.