tag:theconversation.com,2011:/nz/topics/icebergs-73014/articlesIcebergs – The Conversation2023-06-28T15:12:36Ztag:theconversation.com,2011:article/2073552023-06-28T15:12:36Z2023-06-28T15:12:36ZFrom raising the global sea level to crushing life on the seafloor – here’s why you should care about icebergs<figure><img src="https://images.theconversation.com/files/534283/original/file-20230627-23-8yvpno.jpg?ixlib=rb-1.1.0&rect=26%2C13%2C4375%2C2923&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Icebergs in Disko Bay, western Greenland.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/icebergs-disco-bay-near-ilulissat-greenland-1888385068">Chris Christophersen/Shutterstock</a></span></figcaption></figure><p>Late in the evening of April 14 1912, the <a href="https://theconversation.com/titanic-twist-1912-wasnt-a-bad-year-for-icebergs-after-all-25621">RMS Titanic collided with an iceberg</a> in the north-west Atlantic. In just over two and a half hours, the Titanic sank, claiming the lives of 1,514 people.</p>
<p>The Titanic disaster is one good reason to understand icebergs better. But their significance extends far beyond posing a risk to ships and other offshore structures. Icebergs are crucial to monitor because of their profound impact on the natural world and human societies.</p>
<p>Icebergs are formed when chunks of ice break off from the front of glaciers and floating ice shelves. They exist in a range of sizes, from small formations known as “growlers” and “bergy bits” (that extend up to 5 metres above sea level), to larger icebergs aptly referred to as “giants”. </p>
<p>In 2000, one of Antarctica’s largest icebergs, <a href="https://earthobservatory.nasa.gov/images/552/iceberg-b-15-ross-ice-shelf-antarctica">called B-15</a>, had a surface area roughly the same size as Jamaica. Since then, <a href="https://earthobservatory.nasa.gov/images/92238/end-of-the-journey-for-iceberg-b-15z">B-15 has fractured</a> into a number of smaller pieces and most have melted away. </p>
<p>Icebergs that break off from an already floating ice shelf do not displace ocean water when they melt, just as melting ice cubes do not raise the liquid level in a glass. But when an ice shelf collapses, it no longer holds back inland glacial ice. This inland ice will then move faster and can rapidly release new icebergs, which displace ocean water and contribute to sea level rise. </p>
<p>In 2022, Antarctica’s <a href="https://theconversation.com/conger-ice-shelf-has-collapsed-what-you-need-to-know-according-to-experts-180077">Conger ice shelf</a> collapsed. Some of the continent’s other large <a href="https://www.antarcticglaciers.org/glaciers-and-climate/changing-antarctica/shrinking-ice-shelves/ice-shelves/">ice shelves</a> are also thought to be at risk of collapse in the future, particularly those around the unstable West Antarctic ice sheet. The collapse of the West Antarctic ice sheet alone could <a href="https://www.antarcticglaciers.org/question/ice-antarctica-melt-much-global-sea-level-rise-quickly-likely-happen/">raise the global sea level by 3.2 metres</a>. </p>
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<img alt="A glacier calving large chunks of ice into the ocean." src="https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534292/original/file-20230627-15-c2x0zd.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">A chunk of ice breaking off from a glacier in Neko Harbour, Antarctica.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/neko-harbor-glacier-calving-andvord-bay-1556725400">Steve Allen/Shutterstock</a></span>
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<p>Global warming accelerates not only iceberg release, but also the rate at which icebergs melt. As icebergs melt, they release freshwater to the ocean. </p>
<p>In the northern hemisphere, a surplus of freshwater from the Greenland ice sheet in the future has the potential to weaken or even shut down the North Atlantic Conveyor “pump”, which circulates warm tropical waters northwards. If the North Atlantic Conveyor pump is significantly affected, the northern hemisphere could be plunged into <a href="https://www.tandfonline.com/doi/abs/10.1080/00167487.2005.12094137">sub-zero, glacial conditions</a>. </p>
<h2>‘Scouring’ the seabed</h2>
<p>Icebergs are often thought of as floating masses of ice. Yet their undersides regularly come into contact with the seabed, gouging out sediment on the seafloor to form “scour” marks. Some <a href="https://www.int-res.com/abstracts/meps/v186/p1-8/">15–20% of the world’s oceans</a> are affected by this phenomenon.</p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S0277379116303638">Research</a> that I co-authored in 2016 on iceberg scouring in East Greenland, found that icebergs can disturb sediment up to several metres below the seabed. This disturbance poses a risk to offshore marine structures such as buried pipelines and telecommunication cables.</p>
<p>Icebergs can also crush plants and animals when they collide with the seabed. These organisms, such as seagrasses and molluscs, are important stores of carbon in polar regions. In areas of West Antarctica, referred to as <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.13523">“iceberg killing fields”</a>, iceberg scouring may recycle around 80,000 tonnes of carbon back into the atmosphere each year. </p>
<h2>Ocean fertilisers (and polluters)</h2>
<p>But it’s not all bad news. Some icebergs contain substantial amounts of iron-rich sediment, known as “dirty ice”. These icebergs <a href="https://www.nature.com/articles/s41467-019-13231-0">fertilise the ocean</a> by supplying important nutrients to marine organisms such as phytoplankton. </p>
<p>Following the passage of an iceberg, there is an increase in organism growth and levels of chlorophyll (the green pigment in plants used for photosynthesis) in the surrounding water. This can result in vibrant blooms that extract CO₂ from the atmosphere as they grow. </p>
<p><a href="https://www.nature.com/articles/ngeo2633">One study</a> on icebergs in the Southern Ocean found that these blooms can be up to ten times the length of the iceberg and can persist for more than a month. Blooms in the wake of icebergs off Antarctica have the capacity to absorb <a href="https://www.cbc.ca/news/science/icebergs-climate-change-1.3401729#:%7E:text=Ocean%20blooms%20in%20the%20wake,as%20Sweden%20or%20New%20Zealand.">up to 40 million tonnes of carbon</a> each year.</p>
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<a href="https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A satellite image of a phytoplankton bloom in the Ross Sea, Southern Ocean." src="https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534296/original/file-20230627-29-a5yqmx.jpeg?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>
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<span class="caption">January 22, 2011: a phytoplankton bloom in the Ross Sea, Southern Ocean.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/48949/bloom-in-the-ross-sea">Norman Kuring/NASA Goddard Space Flight Center</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<p>But icebergs hold more than just nutrients in their icy structures. Glacier ice may harbour <a href="https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-021-01106-w">ancient bacterial and viral microbes</a>, even including <a href="https://www.tandfonline.com/doi/full/10.1657/1938-4246-44.4.432">buried faecal microorganisms</a>. These microbes will eventually emerge at the glacier’s surface or in icebergs where they will enter natural ecosystems and could pose a threat to human health. </p>
<p><a href="https://journals.sagepub.com/doi/pdf/10.1177/03091333221107376">Research</a> has also identified various other contaminants within glaciers. These include soot, nuclear fallout, potentially toxic elements such as arsenic, mercury and lead, nitrogen-based contaminants such as fertilisers and animal waste, microplastics and persistent organic pollutants such as pesticides and solvents. </p>
<p>Scientists are, however, exploring the possibility of <a href="https://www.nature.com/articles/s41598-022-26952-y#:%7E:text=A%20long%2Dheld%20idea%20is,United%20Arab%20Emirates%20(UAE)">towing icebergs to water-scarce regions</a>. An iceberg holding 20 billion gallons of freshwater could potentially <a href="https://www.theguardian.com/environment/2017/may/05/could-towing-icebergs-to-hot-places-solve-the-worlds-water-shortage">meet the water needs of a million people</a> for five years – provided that the water is uncontaminated. </p>
<p>Icebergs have an impact on our oceans, atmosphere and societies. As the climate emergency intensifies and our glaciers and ice sheets continue to recede, the significance of icebergs will only grow, for better or worse.</p>
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<p class="fine-print"><em><span>Lorna Linch 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>Icebergs don’t just pose a risk to ships – they have a profound impact on the natural world and human societies.Lorna Linch, Principal Lecturer in Physical Geography, University of BrightonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1614932021-05-25T15:01:05Z2021-05-25T15:01:05ZFive satellite images that show how fast our planet is changing<p>You have probably seen satellite images of the planet through applications like Google Earth. These provide a fascinating view of the surface of the planet from a unique vantage point and can be both beautiful to look at and useful aids for planning. But satellite observations can provide far more insights than that. In fact, they are essential for understanding how our planet is changing and responding to global heating and can do so much more than just “taking pictures”. </p>
<p>It really is rocket science and the kind of information we can now obtain from what are called Earth observation satellites is revolutionising our ability to carry out a comprehensive and timely health check on the planetary systems we rely on for our survival. We can measure changes in sea level down to a single millimetre, changes in how much water is stored in underground rocks, the temperature of the land and ocean and the spread of atmospheric pollutants and greenhouse gases, all from space.</p>
<p>Here I have selected five striking images that illustrate how Earth observation data is informing climate scientists about the changing characteristics of the planet we call home.</p>
<h2>1. The sea level is rising – but where?</h2>
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<a href="https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing global sea level rise" src="https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=364&fit=crop&dpr=1 600w, https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=364&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=364&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=457&fit=crop&dpr=1 754w, https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=457&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/402458/original/file-20210524-23-r4zfxc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=457&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 sea is rising quickly – but not evenly.</span>
<span class="attribution"><span class="source">ESA/CLS/LEGOS</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
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<p>Sea level rise is predicted to be one of the most serious consequences of global heating: under the more extreme “business-as-usual” scenario, a two-metre rise would flood 600 million people <a href="https://www.nature.com/articles/s41467-019-12808-z?fbclid=IwAR02eB8HX3vPOgHpQjRRbujjoe0ZW932ziimLBOpJ-3wupL31SYlB81ui_o">by the end of this century</a>. The pattern of sea surface height change, however, is not uniform across the oceans. </p>
<p>This image shows mean sea level trends over 13 years in which the global average rise was about 3.2mm a year. But the rate was three or four times faster in some places, like the south western Pacific to the east of Indonesia and New Zealand, where there are numerous small islands and atolls that are already very vulnerable to sea level rise. Meanwhile in other parts of the ocean the sea level has barely changed, such as in the Pacific to the west of North America.</p>
<h2>2. Permafrost is thawing</h2>
<figure> <img src="https://cdn.theconversation.com/static_files/files/1589/image2-33.gif?1621946141"><figcaption>Source: ESA</figcaption></figure>
<p>Permafrost is permanently frozen ground and the vast majority of it lies in the Arctic. It stores huge quantities of carbon but when it thaws, that carbon is released as CO₂ and an even more potent greenhouse gas: methane. Permafrost stores about <a href="https://www.nature.com/articles/d41586-019-01313-4#:%7E:text=We%20estimate%20that%20abrupt%20permafrost,regions%20that%20will%20thaw%20gradually.">1,500 billion tonnes</a> of carbon – twice as much as in the whole of the atmosphere – and it is incredibly important that carbon stays in the ground.</p>
<p>This animation combines satellite, ground-based measurements of soil temperature and computer modelling to map the permafrost temperature at depth across the Arctic and how it is changing with time, giving an indication of where it is thawing.</p>
<h2>3. Lockdown cleans Europe’s skies</h2>
<figure> <img src="https://cdn.theconversation.com/static_files/files/1590/image3-35.gif?1621946793"><figcaption>Source: ESA</figcaption></figure>
<p>Nitrogen dioxide is an atmospheric pollutant that can have serious health impacts, especially for those who are asthmatic or have weakened lung function, and it can increase the acidity of rainfall with damaging effects on sensitive ecosystems and plant health. A major source is from internal combustion engines found in cars and other vehicles.</p>
<p>This animation shows the difference in NO₂ concentrations over Europe before national pandemic-related lockdowns began in March 2020 and just after. The latter shows a dramatic reduction in concentration over major conurbations such as Madrid, Milan and Paris.</p>
<h2>4. Deforestation in the Amazon</h2>
<iframe src="https://www.esa.int/content/view/embedjw/353312" width="100%" height="360" frameborder="0"></iframe>
<p>Credits: ESA/USGS/Deimos Imaging </p>
<p>Tropical forests have been described as the lungs of the planet, breathing in CO₂ and storing it in woody biomass while exhaling oxygen. Deforestation in Amazonia has been in the news recently because of deregulation and increased forest clearing in <a href="https://www.bbc.co.uk/news/world-latin-america-55130304">Brazil</a> but it had been taking place, perhaps not so rapidly, for decades. This animation shows dramatic loss of rainforest in the western Brazilian state of Rondonia between 1986 and 2010, as observed by satellites. </p>
<h2>5. A megacity-sized iceberg</h2>
<figure> <img src="https://cdn.theconversation.com/static_files/files/1588/image5-39.gif?1621943077"><figcaption>Source: ESA</figcaption></figure>
<p>The Antarctic Ice Sheet contains enough frozen water to raise global sea level by 58 metres if it all ended up in the ocean. The floating ice shelves that fringe the continent act as a buffer and barrier between the warm ocean and inland ice but they are vulnerable to both oceanic and atmospheric warming. </p>
<p>This animation shows the break-off of a huge iceberg dubbed A-74, captured by satellite radar images that have the advantage they can “see” through clouds and operate day or night and are thus unaffected by the 24 hours of darkness that occurs during the Antarctic winter. The iceberg that forms is 1,270 km² in area which is about the same size as Greater London.</p>
<p>These examples illustrate just a few ways in which satellite data are providing unique, global observations of key components of the climate system and biosphere that are essential for our understanding of how the planet is changing. We can use this data to monitor those changes and improve models used to predict future change. In the run up to the vitally important UN climate conference, COP26 in Glasgow this November, colleagues and I have produced a <a href="https://www.gla.ac.uk/media/Media_792662_smxx.pdf">briefing paper</a> to highlight the role Earth observation satellites will play in safeguarding the climate and other systems that we rely on to make this beautiful, fragile planet habitable.</p><img src="https://counter.theconversation.com/content/161493/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 European Commission Horizon2020 Framework Programme and the European Space Agency. </span></em></p>Earth observation satellites can measure millimetre changes in sea level and track deforestation in near-real time.Jonathan Bamber, Professor of Physical Geography, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1449922020-10-05T12:10:13Z2020-10-05T12:10:13ZShrinking glaciers have created a new normal for Greenland’s ice sheet – consistent ice loss for the foreseeable future<figure><img src="https://images.theconversation.com/files/361421/original/file-20201002-20-8jxj4v.jpeg?ixlib=rb-1.1.0&rect=49%2C93%2C3603%2C2305&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As Greenland's glaciers retreat, they are losing ice at a faster and faster rate. </span> <span class="attribution"><span class="source">Michalea King</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Greenland is the largest island on Earth, and about 80% of it is covered by a <a href="https://nsidc.org/cryosphere/quickfacts/icesheets.html">giant sheet of ice</a>. Slowly flowing glaciers connect this massive frozen reservoir of fresh water to the ocean, but because of climate change, these glaciers are rapidly retreating.</p>
<p><a href="https://scholar.google.com/citations?user=1PYqI-4AAAAJ&hl=en&oi=ao">I’m an earth scientist</a> who studies how changes to Greenland’s glaciers affect the stability of the ice sheet as a whole. Healthy glaciers are stable in size and shape and act as drains for the ice sheet, transporting ice into the sea. They maintain a balance where the ice added each year roughly equals the ice lost to the sea. </p>
<p>But because of warming caused by climate change, that dynamic has changed. </p>
<p>For years, scientists have watched as glaciers around the world retreat. But our research has found that the glaciers along the edge of Greenland have retreated so much that they no longer <a href="https://doi.org/10.1038/s43247-020-0001-2">keep the ice sheet that feeds them in balance</a>. </p>
<p>As the glaciers retreat up valleys, they flow faster and bring more ice from inland to the sea. Imagine a traffic jam: When a highway is jampacked with cars – or ice – it flows slowly. But as the jam or glacier gets smaller, the number of cars, or the amount of ice, that can flow by in a given time increases. </p>
<p>Greenland’s ice sheet is now out of balance. The new normal is an <a href="https://doi.org/10.1038/s43247-020-0001-2">annual overall loss of ice</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial view of the edge of the large Jakobshvan Glacier, where ice breaks off into the sea." src="https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361423/original/file-20201002-22-hnuk7b.jpeg?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">The place where glaciers meet the sea – called the calving front – is important for the stability of the entire ice sheet. Jakobshavn Glacier has been retreating for decades.</span>
<span class="attribution"><span class="source">Michalea King</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Changes at the edge, consequences for the whole</h2>
<p>Ice sheets are formed when snowfall accumulates over thousands of years and compresses into layers upon layers of ice. But ice is not a perfectly rigid material – it behaves kind of like an <a href="https://doi.org/10.1002/2015EF000301">extra-thick yet brittle honey</a>. </p>
<p>Once an ice sheet becomes tall enough, the ice begins to flow outward because of its own weight. This ice is funneled down valleys toward the ocean, forming fast–flowing outlet glaciers. These glaciers can move as much as <a href="https://doi.org/10.5194/tc-8-209-2014">10 miles</a> per year.</p>
<p>Although glaciers comprise only a narrow region at the edge of the ice sheet, they play a huge role in controlling how rapidly ice is drained from the sheet into the ocean. Generally, a glacier that extends a long distance through a valley <a href="https://doi.org/10.1029/JB094iB04p04071">will move more slowly</a> and drain less ice from the ice sheet than if it were shorter. </p>
<p>Most of Greenland’s glaciers end at the sea, where ocean water melts and weakens the ice until it breaks off in pieces that dramatically fall into the North Atlantic. If ice is lost at the front of the glacier faster than it is replenished by upstream ice, the glacier will recede inland. This is called glacial retreat. </p>
<p>Retreat not only shortens the length of the glacier but also reduces the <a href="https://doi.org/10.1038/ngeo394">friction between the ice and surrounding valleys</a>. With less surface area of ice touching the ground, the ice can flow faster. Much like a shrinking traffic jam, sustained glacier retreat results in faster-flowing glaciers that <a href="https://doi.org/10.3189/002214308786570908">drain the ice sheet above more rapidly</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map showing the extent of glacial retreat since 1990." src="https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=602&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=602&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=602&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=757&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=757&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361422/original/file-20201002-13-1dijqh9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=757&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 blue line shows the current boundary between the Jakobshavn Glacier (right side, light gray) and the floating ice (center, white) between the valley walls (top and bottom, dark gray). The other colored lines show where this boundary was in previous years.</span>
<span class="attribution"><span class="source">Michalea King</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>A persistent state of loss</h2>
<p>Ocean and air temperatures have strong effects on glaciers. Both <a href="https://doi.org/10.1029/2018GL078024">ocean</a> and <a href="https://doi.org/10.1007/s10712-013-9261-z">air temperatures</a> are rising.</p>
<p>For Greenland’s glaciers, the warming ocean is the biggest cause of glacial retreat. On average the glaciers have retreated about <a href="https://doi.org/10.1038/s43247-020-0001-2">3 kilometers since the mid-1980s</a>, with most of this retreat occurring between 2000 and 2005.</p>
<p>My colleagues and I used thousands of satellite images to measure changes in length, thickness and flow speed of Greenland’s glaciers. With this information, we found two important things: Glacial retreat is accelerating, and the ice sheet is losing an astonishing – and also increasing – amount of ice each year.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Michalea King, a glacier researcher, stands in front of bay full of icebergs." src="https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361425/original/file-20201002-14-1td91n8.jpeg?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">The glaciers have retreated so much that the amount of ice they lose exceeds how much ice is added each year.</span>
<span class="attribution"><span class="source">Santiago de la Peña</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our team found that today, the glaciers drain <a href="https://doi.org/10.1038/s43247-020-0001-2">14% more ice from the ice sheet annually</a> – approximately 500 billion metric tons – than they did on average between 1985 and 1999. This faster flow is causing the ice sheet that covers most of Greenland to shrink, but it has also changed the dynamic of the entire system. </p>
<p>The ice sheet is now in a new, unbalanced state of persistent mass loss. Before the year 2000, ice loss roughly equaled the ice added from snowfall, so the ice sheet was stable. Now, ice mass losses consistently exceed mass gains – even in the coolest years of relatively high snow accumulation. The glaciers used to act as an important traffic jam, keeping ice loss in check. Now, however, traffic flows more freely and the ice is able to more easily flow away from the ice sheet. </p>
<p>Unfortunately, warmer air temperatures have also <a href="https://doi.org/10.1038/s41586-018-0752-4">increased surface melt</a>, resulting in less snow now accumulating on Greenland. Given all these factors, my colleagues and I now estimate that the ice sheet may see a mass gain year <a href="https://doi.org/10.1038/s43247-020-0001-2">only once a century</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial view of a pond on the top of a glacier formed by melting ice." src="https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/361426/original/file-20201002-24-fwt0zp.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Eventually, the ice sheet will become completely landlocked, and only ice melt and snow accumulation will determine then whether it grows or disappears completely.</span>
<span class="attribution"><span class="source">Michalea King</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>In serious trouble, but not yet doomed</h2>
<p>Our study showed how widespread retreat drove both an increase in glacier discharge and a shift to persistent ice sheet mass loss. But this doesn’t mean the ice sheet is doomed. Continued retreat and further increases in discharge are limited by topography. </p>
<p>[<em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>.]</p>
<p>Over the next several centuries, the glaciers may retreat onto higher ground and eventually form a completely <a href="https://doi.org/10.1126/sciadv.aav9396">landlocked ice sheet with minimal flow</a> – essentially a large chunk of ice sitting on top of Greenland with no glaciers to drain it. Under this future scenario, the balance of the ice sheet would be determined only by surface changes – snow accumulation and surface melt. This loss of ice would equal <a href="https://doi.org/10.1126/sciadv.aav9396">meters of sea level rise</a>.</p>
<p>At this point, the fate of the ice sheet simply depends on whether it is melting faster than it grows from snowfall. In a warm world where climate change is not addressed, the ice sheet will slowly melt and ultimately disappear. But if climate change is controlled and cooler temperatures are maintained for a prolonged period, it is possible that the Greenland ice sheet could regrow.
That day may be hundreds of years into the future, but it is actions made today that will decide the fate of Greenland’s ice sheet.</p><img src="https://counter.theconversation.com/content/144992/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michalea King received partial funding from NASA during her graduate studies to complete this work. </span></em></p>Greenland’s glaciers have retreated so far that they can no longer support the ice sheet that feeds them. The ice sheet system has reached a new normal of consistent annual ice loss.Michalea King, Postdoctoral Climate Science Researcher, The Ohio State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1194992019-07-22T10:55:31Z2019-07-22T10:55:31ZWaiting for an undersea robot in Antarctica to call home<figure><img src="https://images.theconversation.com/files/281448/original/file-20190626-76705-w53a62.jpg?ixlib=rb-1.1.0&rect=0%2C310%2C5184%2C3135&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One of two underwater gliders is deployed from a research ship into Antarctic waters.</span> <span class="attribution"><span class="source">NOAA</span></span></figcaption></figure><p>“Call! Just call!” I think loudly in my head. “Did something happen? Are you okay?”</p>
<p>I might seem like a worried parent waiting for a teenager to report in from an unsupervised outing. Rather, I’m a <a href="https://www.linkedin.com/in/jenmariewalsh">research biologist</a> with the Antarctic Ecosystem Research Division at the National Oceanic and Atmospheric Administration. It’s late February 2019, and I am waiting for an autonomous underwater glider in Antarctica to surface and call me via satellite, so I can give it new diving instructions. The longest it’s supposed to go without surfacing is eight hours, and it’s now been nine.</p>
<p>Did it get stuck under an iceberg? An underwater ledge? I feel so helpless; I’m 9,000 miles away in San Diego and all I can do is chew my fingernails and think, “No. This can’t happen. We can’t lose this glider so close to the end.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=565&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=565&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=565&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=711&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=711&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281837/original/file-20190628-94720-cx387f.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=711&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 survey area where gliders measured Antarctic krill populations.</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Our research team is two-and-a-half months into a three-month-long mission just north of the Antarctic Peninsula. This is our first time deploying gliders so far from home, and our hope for a successful field season – not to mention a great deal of research – depends on recovering the two gliders our group deployed in December 2018. The gliders are now full of oceanographic data that will help us provide scientific advice on how best to conserve the Antarctic ecosystem as the area around the peninsula warms faster than almost any other region on Earth, which may adversely affect the animals that live there.</p>
<h2>9 hours, 30 minutes: No call</h2>
<p>For over 30 years, the <a href="https://swfsc.noaa.gov/textblock.aspx?id=551&ParentMenuId=42">NOAA group I’m part of</a> has conducted studies to estimate how many Antarctic krill, small shrimp-like creatures that support the diverse Antarctic food web, live around the Antarctic Peninsula.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=467&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=467&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=467&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=586&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=586&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281449/original/file-20190626-76734-1ycpivt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=586&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Antarctic krill, <em>Euphausia superba</em>, can grow up to about 2.5 inches long.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Krill666.jpg">Uwe Kils/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Krill feeds penguins and seals that breed in this area every summer and whales and fishes that feed here year-round, while also supporting a major fishery. You may have seen bright-red dietary supplements made from krill oil prominently displayed at the pharmacy. Our data help establish catch limits for the krill fishery, ensuring enough krill remain in the ocean to maintain the population after all people and animals take what they need to make a living. Without good data to support fishery-management decisions, krill fishing could <a href="https://www.ccamlr.org/en/fisheries/krill-%E2%80%93-biology-ecology-and-fishing">undermine the food web</a> for which Antarctica is so well known, as demand for supplements and other <a href="https://bestmarketherald.com/krill-oil-market-demand-expected-to-raise-by-dietary-supplements-segment-in-upcoming-years/">krill products surges</a>.</p>
<h2>10 hours: No call</h2>
<p>Until three years ago, my program chartered a research vessel for a month each year to sail around the Antarctic Peninsula and <a href="https://swfsc.noaa.gov/contentblock.aspx?ID=14326&ParentMenuId=42">estimate the biomass of krill</a>. But after 2016, rising vessel costs eliminated our surveys. For our program to continue, we had to find a creative way to collect our data in Antarctica without actually going to Antarctica. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281776/original/file-20190628-94724-w5a3pn.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">An autonomous glider in the ocean.</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Our solution was to use autonomous underwater gliders, which can be deployed in just a few hours by a small team from a ship in Antarctica, and then recovered months later. Gliders can dive to 3,000 feet, cover thousands of miles and follow commands from anywhere in the world with a laptop and an internet connection. Their batteries last six months, which means that they can collect much more data for much less money than a bunch of scientists on a research vessel. </p>
<p>The gliders resemble torpedoes in appearance, but contain three massive batteries and an array of scientific sensors that collect much of the same data we used to collect from a ship. Although the gliders are able to transmit small amounts of data via satellite throughout the deployment, the most valuable data are stored on the glider. If we lose a glider, which is always a possibility when you let something roam free in the ocean unattended for months, then we also lose the data.</p>
<p>We had effectively replaced ourselves with drones. But would they work?</p>
<h2>12 hours: No call</h2>
<p>For most of our team, the transition just a year ago from annual research voyages to the aquatic versions of C-3PO and R2-D2 was exciting. Secretly, though, I was terrified. I had spent my career as a scientist collecting krill samples from research vessels for biochemical analyses of their tissues. Suddenly I found myself ousted by oceanographic robots full of cables, wires, circuit boards and all sorts of other technological gadgetry.</p>
<p>These are not what you’d call smart robots. A bit like human toddlers, they have some degree of self-awareness, but would destroy themselves without semi-constant monitoring and instructions on how deep to dive or where to go. Outside supervision is especially important in the Southern Ocean, which is full of seamounts, canyons, strong currents and, most importantly, icebergs. </p>
<p>You can’t glider-proof the ocean the way you can baby-proof a house, so I had to forget everything I knew about biochemistry and learn as much as I could about glider piloting in 10 short months.</p>
<h2>13 hours: No call</h2>
<p>All that training and practice felt like 10 minutes by the time we finally packed up the gliders and shipped them to the Southern Hemisphere for their first Antarctic deployments. The commands for how deep to dive and where to go seemed simple enough, but the gliders responded as unpredictably as the ocean itself. </p>
<p>A near-disastrous practice deployment in San Diego revealed how slowly they maneuver, particularly in strong currents. Piloting them felt like trying to drive a remote-control semi-truck through a go-kart course, which reinforced our apprehension about driving these things through the ocean all the way across the planet, in one of the most remote and treacherous oceans on Earth.</p>
<p>Never mind the wind and the currents and the icebergs. What made this deployment far scarier was that if things started to go horribly wrong, we had no way to get the gliders back. It was like dropping a toddler off at college on another continent: What if he needs you and you can’t get to him?</p>
<h2>14 hours: No call</h2>
<p>Almost exactly 10 months from our first day of glider training, we carried the gliders across the Drake Passage on a research vessel bound for the Antarctic Peninsula. The deployments were flawless, and over the next few days, our confidence began to build. We quickly learned that icebergs were enemy number one, and they were formidable opponents. Satellite images of icebergs were <a href="https://www.polarview.aq/antarctic">available every couple of days</a>, and we overlaid maps of planned glider tracks onto those images so we could steer the gliders around any ice in their way. The trouble was, even the newest images we received were already a day old, and the ice had already moved.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=312&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=312&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=312&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=392&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=392&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281839/original/file-20190628-94708-1yfhkyg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=392&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On this chart of the South Shetland Islands, one intended glider path is marked in straight gray lines. Circled in red in the middle is the iceberg the researchers called ‘Yacu.’</span>
<span class="attribution"><span class="source">NOAA</span></span>
</figcaption>
</figure>
<p>Smaller icebergs were usually avoidable, but around three weeks into the deployment, “Yacu” appeared on the scene. Inspired by a <a href="http://www.salem-news.com/articles/august162010/monster-amazon-ta.php">mythological South American snake</a> that eats everything in its way, that was the nickname we gave a 12.5-mile-wide iceberg from the Weddell Sea that drifted right into the path of one of the gliders. Yacu stuck around for the rest of the deployment, every few days spawning smaller (but still huge) icebergs that posed a constant and unpredictable threat to gliders already at the mercy of currents, tides and wind.</p>
<p>If a glider gets trapped under an obstacle and senses that it’s been underwater for too long, it drops an emergency weight to rocket itself to the surface for an immediate recovery. Once a glider drops its weight, it can’t dive anymore. So if it is trapped under ice, it’s likely to stay trapped under ice. And one way to know if a glider is trapped is that it stops calling in, because it can connect to satellites only when it’s at the surface.</p>
<h2>15 hours: No call</h2>
<p>And then…</p>
<p>Ding ding! Ding ding! My laptop screams at me after 16 long hours: The glider is at the surface.</p>
<p>It is well past 9 p.m., but every member of our five-person team has been glued to a computer since early afternoon, and we collectively sigh with relief. We now think the glider probably surfaced after the first eight hours, failed to connect to the satellite and resumed diving, which can occasionally happen. The reason for the gap is unimportant compared to our elation. A couple of weeks later, we successfully recovered both gliders on schedule and completed our first autonomous Antarctic field season. </p>
<p>One key finding is that we can, in fact, replace a vessel-based fishery assessment with a glider-based one in less than a year. With gliders, we can get krill biomass estimates comparable to those we would expect from a ship. That means we can use gliders to continue to provide critical data for managing the krill fishery.</p>
<p>This is a profound accomplishment for us and for NOAA, and it also has far-reaching promise for the future of fisheries research globally. The cost of science keeps going up, and autonomous instruments offer an affordable way to collect critical data for effectively managing ocean resources and conserving fragile marine ecosystems worldwide. </p>
<p>Our gliders are like toddlers in one final way: They’re advanced technology, yet they’re still in their infancy. Their ongoing usefulness to understand our changing planet in real time will depend on new sensors and instruments yet to be developed. What we accomplished is only the the tip of Yacu compared to what the future of autonomous oceanographic research holds.</p><img src="https://counter.theconversation.com/content/119499/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Walsh is employed and funded by the U.S. National Oceanic and Atmospheric Administration. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect the views of NOAA or the Department of Commerce.</span></em></p>Sending autonomous vehicles to the Southern Ocean can be fraught with anxiety, especially if one of them doesn’t make radio contact when it’s supposed to.Jennifer Walsh, Research Biologist, National Oceanic and Atmospheric AdministrationLicensed as Creative Commons – attribution, no derivatives.