tag:theconversation.com,2011:/ca/topics/glacial-retreat-74896/articlesGlacial retreat – The Conversation2024-03-05T21:00:26Ztag:theconversation.com,2011:article/2243732024-03-05T21:00:26Z2024-03-05T21:00:26ZFrozen in time: old paintings and new photographs reveal some NZ glaciers may soon be extinct<figure><img src="https://images.theconversation.com/files/579425/original/file-20240303-30-xkp27s.jpeg?ixlib=rb-1.1.0&rect=12%2C64%2C8502%2C3052&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Freshly exposed bedrock at the terminus of Brewster Glacier in March 2023.</span> <span class="attribution"><span class="source">Andrew Lorrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>As the austral summer draws to a close, we are preparing to fly over the Southern Alps to survey glaciers. This annual flight supports the longest scientific study of Aotearoa New Zealand’s icescapes – and it shows that all of our glaciers have retreated since 1978.</p>
<p>This year’s survey comes on the heels of the <a href="https://wmo.int/news/media-centre/wmo-confirms-2023-smashes-global-temperature-record">warmest year on record globally</a> and the <a href="https://niwa.co.nz/climate/summaries/annual-climate-summary-2023#">second warmest for New Zealand</a>, which produced extreme weather events and impacts that still cut deep for many local communities. </p>
<p>Despite strong El Niño conditions in the Pacific this season, which typically <a href="https://www.nature.com/articles/ncomms14202">boost ice volume</a>, we expect the recent heat grilling the glaciers will have had a grim effect. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/sboyVimLwY0?wmode=transparent&start=290" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Our work monitoring ice in the Southern Alps and central North Island shows many small glaciers are approaching an extinction horizon.</span></figcaption>
</figure>
<p>The 46-year record of end-of-summer glacier images is incredibly valuable because it contains irrefutable <a href="https://theconversation.com/a-birds-eye-view-of-new-zealands-changing-glaciers-97074">visual evidence of climate change</a>. We can see how glaciers are changing from year to year, with extremely hot years such as 2023 standing out clearly. </p>
<p>But our insights aren’t limited to images of glaciers taken from light aircraft. We can also learn from historic paintings of New Zealand’s mountain landscapes. </p>
<h2>Portraits of past climate</h2>
<p>Old paintings with glaciers are common for the European Alps, where many artists lived and visited. But similar offerings are relatively rare for our part of the world.</p>
<p>What’s remarkable for New Zealand is that some of these works of art were produced without the artist ever seeing the glaciers. </p>
<p>We recently scrutinised the artistic vistas painted by <a href="https://teara.govt.nz/en/biographies/1g25/gully-john">John Gully</a> to see if they were true to the real landscapes. Gully based his works on field sketches by <a href="https://teara.govt.nz/en/biographies/6h17/haast-julius-von">Julius Haast</a>, one of the first scientists to formerly recognise widespread glaciation in New Zealand. </p>
<p>Gully’s paintings show features that can be linked to glacial landforms we can see today, including moraines (rocks deposited by a glacier, typically at its edges), outwash fans (sediment deposited by braided rivers fed by a melting glacier) and trimlines (lines that mark a glacier’s earlier, higher position in a valley). </p>
<p>Many of those features in the paintings have ice in direct contact with them, showing how accurately field scientists and artists depicted glaciers at the time. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=305&fit=crop&dpr=1 600w, https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=305&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=305&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=383&fit=crop&dpr=1 754w, https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=383&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/578079/original/file-20240226-27-zie9ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=383&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">John Gully, On the Great Godley Glacier [1862], watercolour. Lakes and sediment now exist in these valleys where glaciers used to flow.</span>
<span class="attribution"><span class="source">Alexander Turnbull Library</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Gully’s paintings were intended to convey the dramatic scale of a mysterious land located far away from industrialised 19th-century society. Serendipitously, for contemporary scientists, comparing these artworks with current photos vividly shows the magnitude of ice loss that has occurred since the mid-1800s. </p>
<p>The perspective we get from Gully’s paintings concurs with studies that place the <a href="https://www.science.org/doi/10.1126/science.1169312">timing of ice retreat</a> as being already underway in the mid-1800s. Prior to this time, known commonly as the Little Ice Age, New Zealand <a href="https://link.springer.com/article/10.1007/s00382-013-1876-8">experienced cooler temperatures</a> between about 1450 and 1850. </p>
<p>Modelling ice volume loss using these Little Ice Age landforms provides a benchmark. It illustrates that recent changes have occurred in a geological instant and that the <a href="https://www.nature.com/articles/s41598-020-70276-8">peak summer flows from glaciers</a> that helped create the braided river systems so typical of the South Island landscape are in the past. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-climate-change-made-the-melting-of-new-zealands-glaciers-10-times-more-likely-143626">How climate change made the melting of New Zealand's glaciers 10 times more likely</a>
</strong>
</em>
</p>
<hr>
<h2>Accelerating pace of glacier retreat</h2>
<p>Recent glacier changes are occurring ever more quickly. The long-term photographic record from the Southern Alps shows an <a href="https://www.cambridge.org/core/journals/journal-of-glaciology/article/southern-alps-equilibrium-line-altitudes-four-decades-of-observations-show-coherent-glacierclimate-responses-and-a-rising-snowline-trend/44DD090754DAEB558AFFF4D31BD734B1">acceleration</a> of the pace at which snowlines rise due to climate warming. </p>
<p>For a glacier to exist, average summer temperatures must be cool enough for the summer snowline to remain below mountain tops so ice can accumulate. We now observe that ice is disappearing from mountains which held small amounts during the late 1970s. Glaciers there are going extinct.</p>
<p>Combining long-term snowline observations with direct field measurements of <a href="https://www.antarcticglaciers.org/glacier-processes/mass-balance/#">glacier mass balance</a> and <a href="https://www.cambridge.org/core/journals/journal-of-glaciology/article/using-structure-from-motion-photogrammetry-to-measure-past-glacier-changes-from-historic-aerial-photographs/18ACF49DFC0EC82A02655108A9E3453C">3D models of ice volume change</a> gives a good synopsis of how things have changed and a sense of things to come. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cop28-earths-frozen-zones-are-in-trouble-were-already-seeing-the-consequences-218119">COP28: Earth's frozen zones are in trouble – we're already seeing the consequences</a>
</strong>
</em>
</p>
<hr>
<p>We estimate at least 13 trillion litres of water (in the form of ice) has been lost from the Southern Alps since 1978. This is equivalent to the basic water needs for all New Zealanders during that time. </p>
<p>The regions around the central Southern Alps that hold many small glaciers are experiencing accelerated ice loss. Some areas, like Southland and Otago, have small glaciers that are rapidly approaching an extinction horizon. And once they pass it, we are not likely to see them again. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579415/original/file-20240303-18-6z9u00.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Brewster Glacier in Mt Aspiring National Park has the longest record of mass balance measurements. Using snowstakes, we document its retreat due to warming temperatures.</span>
<span class="attribution"><span class="source">Andrew Lorrey</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The central North Island also hosts a number of <a href="https://www.rnz.co.nz/national/programmes/ourchangingworld/audio/2018783809/glaciers-as-barometers-of-climate-change54">small glaciers on Mt. Ruapehu</a> that feed into the headwaters of the Waikato and Whanganui rivers. Glaciers there were <a href="https://www.tandfonline.com/doi/abs/10.1080/00288306.2020.1811354">originally mapped</a> in the mid-20th century, and again in 1978, 1988 and 2016. A recent photographic capture of Mt Ruapehu reflects a dire situation, indicating glaciers are fast approaching extinction. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=706&fit=crop&dpr=1 600w, https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=706&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=706&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=887&fit=crop&dpr=1 754w, https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=887&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/579099/original/file-20240301-16-h982sz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=887&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This aerial image of the Mt Ruapehu summit region shows the earliest complete glacier survey from the Randolph Glacier Inventory (1978, white-dashed line) and an assessment from 2022 (yellow-dashed line).</span>
<span class="attribution"><span class="source">Shaun Eaves</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Environments and ethics</h2>
<p>New Zealand’s diminishing glaciers and loss of ice across Earth are largely carrying on unabated. These changes are primarily caused by rising temperatures driven by <a href="https://www.nature.com/articles/s41558-020-0849-2">human activities that produce greenhouse gas emissions</a>. </p>
<p>The <a href="https://gml.noaa.gov/ccgg/trends/weekly.html">global increase in atmospheric carbon dioxide</a> continues undiminished. This needs to change soon and rapidly to protect many of our glaciers. </p>
<p>We face particularly serious ethical questions with respect to Mt Ruapehu’s glaciers. They help sustain the Whanganui River Te Awa Tupua, which has been <a href="https://www.legislation.govt.nz/act/public/2017/0007/latest/whole.html">granted the rights of a living entity</a>. The glaciers’ ongoing retreat – and possible extinction – highlights our collective responsibilities for doing simultaneous harm to the environment and people.</p>
<hr>
<p><em>The authors acknowledge Rebekah Parsons-King at NIWA for her work on the Glacier Extinction Horizons video. We also thank Brian Anderson for his long-term leadership on the Brewster Glacier snowstakes programme, and Pascal Sirguey for his work calculating mass balance for Brewster Glacier.</em> </p>
<hr><img src="https://counter.theconversation.com/content/224373/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Lorrey receives funding from NIWA's Strategic Science Investment Fund, which supports the annual Southern Alps glacier and snowline survey. </span></em></p><p class="fine-print"><em><span>George Hook, Lauren Vargo, and Shaun Eaves 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>An estimated 13 trillion litres of ice has already been lost from glaciers in New Zealand’s Southern Alps since 1978. Several are now approaching extinction.Andrew Lorrey, Principal Scientist & Programme Leader of Southern Hemisphere Climates and Environments, National Institute of Water and Atmospheric ResearchGeorge Hook, Research Associate (in process), Canterbury MuseumLauren Vargo, Research Fellow, Antarctic Research Centre, Te Herenga Waka — Victoria University of WellingtonShaun Eaves, Senior Lecturer in Physical Geography, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1898412022-09-12T18:06:41Z2022-09-12T18:06:41ZCulpability for the Pakistan floods rests with the Pakistani government and rich countries<figure><img src="https://images.theconversation.com/files/484115/original/file-20220912-22-ndg083.jpg?ixlib=rb-1.1.0&rect=0%2C678%2C4669%2C2574&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A group of men sit in floodwater in Pakistan's southwestern Balochistan province, Sept. 3, 2022.</span> <span class="attribution"><span class="source">(AP Photo/Zahid Hussain)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/culpability-for-the-pakistan-floods-rests-with-the-pakistani-government-and-rich-countries" width="100%" height="400"></iframe>
<p>Nearly a <a href="https://www.npr.org/sections/pictureshow/2022/08/30/1119979965/pakistan-floods-monsoon-climate">third of Pakistan</a> still remains submerged after catastrophic flooding. The country’s administration has <a href="https://www.theguardian.com/world/2022/aug/30/pakistan-monsoon-on-steroids-flooding-warning-antonio-guterres">denied responsibility</a> for the crisis and blamed wealthier nations that produce the <a href="https://www.pbs.org/newshour/science/climate-change-caused-by-wealthy-nations-creates-harm-for-poorer-study-says">bulk of global carbon emissions</a> for the unfolding climate disaster.</p>
<p>Rich nations must be <a href="https://www.thenewhumanitarian.org/interview/2022/1/31/rich-countries-owe-rest-of-world-climate-justice-reparations">held accountable</a> and humanitarian aid should be redefined as <a href="https://www.motherjones.com/environment/2020/11/the-case-for-climate-reparations/">climate reparations</a>. The <a href="https://www.theguardian.com/environment/2022/jul/21/climate-emergency-is-a-legacy-of-colonialism-says-greenpeace-uk">colonial legacy of climate change</a> must also be recognized. However, the Pakistani state, too, remains culpable for the dispossession of its people in the wake of the floods.</p>
<p>Like many countries, Pakistan’s population centres are <a href="https://openknowledge.worldbank.org/handle/10986/11746">based around its river systems</a>. Just a few weeks ago, I spoke with Ali, a resident of northwestern Pakistan. He described how his family has been struggling to meet their daily expenses amidst <a href="https://tribune.com.pk/story/2373389/inflation-breaks-all-records-climbs-to-4458">record-high inflation</a>. Since then, the floods have <a href="https://www.france24.com/en/live-news/20220831-heavenly-pakistan-mountain-town-becomes-site-of-ruin">destroyed his village</a> and he is currently in a <a href="https://www.bloomberg.com/news/articles/2022-08-30/half-a-million-forced-into-camps-as-flooding-ravages-pakistan">displacement camp</a>. Twelve years ago, Ali’s family was similarly forced into a camp where I first met him. </p>
<p>This is not the first time Pakistan has experienced flooding of this scale. In 2010, <a href="https://yaleclimateconnections.org/2022/08/cruel-echoes-of-a-2010-disaster-in-pakistans-catastrophic-2022-floods/">large parts of the country were also inundated</a>. I worked in the disaster response following the floods and have since <a href="https://doi.org/10.25071/2292-4736/38546">conducted research with affected communities</a> across the country.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A aerial photo of a flooded town." src="https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483318/original/file-20220907-18-ennilw.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">Homes are surrounded by flood waters in Jaffarabad, a district of Pakistan’s southwestern Balochistan province, Sept. 1, 2022.</span>
<span class="attribution"><span class="source">(AP Photo/Zahid Hussain)</span></span>
</figcaption>
</figure>
<p><a href="https://www.dawn.com/news/1707390/pakistans-history-of-disasters-and-the-lessons-we-fail-to-learn">Important lessons</a> were learned from the floods in 2010. Unfortunately, <a href="https://www.dawn.com/news/1708388?fbclid=IwAR1XmudBM7s1_4yucwxZOKzdynFCHfjb_XysCCTwdHtGkehw_IdULPq5OtA">authorities have failed</a> to use them to shape national policies. </p>
<h2>Marginalized areas hardest hit</h2>
<p>Most notably, the devastation from the floods is taking place in some of the country’s poorest and politically repressed regions, such as Balochistan, where an <a href="https://www.aljazeera.com/program/al-jazeera-world/2012/1/9/balochistan-pakistans-other-war">armed insurgency against state oppression is ongoing</a>. Images of inundated villages cycle with images of <a href="https://www.aljazeera.com/podcasts/2022/5/4/why-are-people-disappearing-in-balochistan">disappeared activists and intellectuals</a>.</p>
<p>Southern Punjab, another heavily impacted region, is also marked by <a href="https://hrcp-web.org/hrcpweb/state-must-address-south-punjabs-long-standing-grievances/">uneven development and inequality</a>. </p>
<p><a href="https://policy-practice.oxfam.org/resources/my-land-my-right-putting-land-rights-at-the-heart-of-the-pakistan-floods-recons-133790/">Insecure land rights</a> were flagged as a significant impediment to disaster recovery after the floods in 2010.</p>
<p>In my work with the United Nations, I have argued that <a href="https://www.unescap.org/publications/accelerating-progress-empowered-inclusive-and-equal-asia-and-pacific">empowerment should be at the heart of climate action</a>, of which security of land tenure is key. </p>
<p>Little progress has been made since then to strengthen land tenure. <a href="https://www.oxfam.org/en/research/uneven-ground-land-inequality-heart-unequal-societies">Land tenure</a> is about the relationship between people and the land where they live and work. In Pakistan, land ownership is deeply <a href="https://www.routledge.com/Politics-Landlords-and-Islam-in-Pakistan/Martin/p/book/9780815392989">embedded with political patronage</a>.</p>
<p>Many in the heavily affected provinces are <a href="https://internationalviewpoint.org/spip.php?article5989">peasant farmers</a> who work for landed elites. Many of these elites <a href="https://www.himalmag.com/the-eclipse-of-feudalism-in-pakistan/">consolidated their hold over land and political power under the British</a> as a reward for facilitating colonial rule.</p>
<p>Contract farmers pay rent to landowners in exchange for the right to stay and plant crops. There is little incentive for the landed class to make any improvements to the land that could mitigate the impacts of flooding. Farmers who rent that land are not allowed to make significant changes.</p>
<p>Those with land tenure, however, more effectively utilize reconstruction assistance to build resilient housing following floods and earthquakes in the country.</p>
<h2>Climate action needs investment and empowerment</h2>
<p>Despite a disaster management authority at the federal and provincial levels, <a href="https://www.thenewhumanitarian.org/news-feature/2022/09/05/Pakistan-floods-urgent-questions-climate-crisis">disaster preparedness and mitigation</a> have not been prioritized. The country’s <a href="https://mocc.gov.pk/SiteImage/Policy/NCCP%20Report.pdf">National Climate Policy</a> details the necessity of early warning systems, disaster-resilient infrastructure, and evacuation plans. These recommendations have yet to be implemented.</p>
<p>The destructive effects of the flooding are exacerbated by <a href="https://foreignpolicy.com/2022/09/01/pakistan-flooding-crisis-climate-change-governance/">years of poor governance</a>. Underdevelopment has become a chronic problem in flood-prone regions. And due to the absence of zoning or relocation policies, communities continue to reside in marginal areas dangerously close to waterways, accumulating the recurring costs of climate change. Where laws exist, <a href="https://tribune.com.pk/story/2374352/floods-largely-damage-riverbank-structures">enforcement</a> has been difficult.</p>
<p>Some of the most crucial lines of defence against flooding are <a href="https://www.france24.com/en/live-news/20220828-flood-fate-of-thousands-lies-with-colonial-era-pakistan-barrage">colonial-era projects,</a> many of which are in a state of disrepair.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A line of people standing in water." src="https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=488&fit=crop&dpr=1 754w, https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=488&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/483315/original/file-20220907-9722-29nv9f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=488&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">People walk through flood waters to receive aid in Pakistan, Sept. 7, 2022. Despite a disaster management authority at the federal and provincial levels, disaster preparedness has not been prioritized.</span>
<span class="attribution"><span class="source">(AP Photo/Fareed Khan)</span></span>
</figcaption>
</figure>
<h2>Reparations and accountability</h2>
<p>Pakistan omits less than one per cent of global emissions but is among the <a href="https://www.concern.net/news/countries-most-affected-by-climate-change">top 10 countries</a> most affected by climate change. The Pakistani Minister of Climate Change has argued that wealthier countries <a href="https://www.theguardian.com/world/2022/sep/04/pakistan-floods-reparations-climate-disaster">owe reparations to countries facing climate disaster</a>.</p>
<p>Climate reparations were a <a href="https://climatechangenews.com/2021/11/12/climate-reparations-crunch-issue-cop26-goes-overtime/">contentious issue at the COP26 summit</a> in Glasgow last year. The U.S. and EU opposed climate reparations.</p>
<p>While climate reparations from the global north may assist Pakistan in recovering from the current crisis, <a href="https://www.tanqeed.org/2014/09/we-should-be-resettled-there/">structural change is needed</a> to prepare the country for the next climate catastrophe. This requires substantial <a href="https://www.bloomberg.com/opinion/articles/2022-08-30/pakistan-could-have-averted-its-climate-catastrophe">investments in climate-resilient infrastructure and poverty reduction</a>.</p>
<p>Pakistan spends billions on servicing debts to foreign lenders. It paid <a href="https://www.dawn.com/news/1705141">$15 billion</a> on payments this year alone. That is over <a href="https://tribune.com.pk/story/2298691/debt-servicing-surges-to-rs21tr">80 per cent of its total tax revenue</a>.</p>
<p>Ammar Ali Jan, a member of the <a href="https://twitter.com/haqooq_e_khalq">Haqooq-e-Khalq Party</a> in Pakistan, argues that the twin crises of indebtedness and climate catastrophe <a href="https://jacobin.com/2022/09/floods-pakistan-natural-disaster-global-south-climate-crisis/">mean we need to change the narrative on climate change</a>. The grassroots collective aims to hold the Pakistani government accountable for rights promised in the country’s constitution. </p>
<p>There are growing calls for <a href="http://cadtm.org/Double-penalty-for-Pakistan-drowning-in-floods-and-debts">debt cancellation</a> as a form of climate reparation. Similar calls were <a href="https://www.oxfam.org/fr/node/9654">made after the floods in 2010</a>.</p>
<p>Frames of <a href="https://www.ictj.org/what-transitional-justice">transitional justice</a> used to pursue accountability following war and conflict <a href="https://doi.org/10.1093/ijtj/ijx024">should also be used in contexts of disasters</a>.</p>
<p>Climate reparations make sense for Pakistan because of the much <a href="https://www.theguardian.com/commentisfree/2022/aug/31/flooding-pakistan-britains-imperial-legacy?CMP=Share_iOSApp_Other">longer history of colonial exploitation</a>. Climate reparations are also colonial reparations.</p>
<p>It won’t be surprising that national authorities, <a href="https://doi.org/10.1080/09614524.2021.1911939">humanitarians</a>, and high carbon emitters will all be on the list of those culpable for the floods in Pakistan if such mechanisms are implemented.</p>
<p>Conversations on climate reparations should be pursued in relation to Pakistan’s internal record of letting its people down. These two aspects cannot be disentangled but must be viewed together through the prism of justice and accountability.</p>
<p>While the lives lost and affected can <a href="https://muse.jhu.edu/article/615675">never be fully restored</a>, centring accountability and empowerment in reconstruction efforts offer a path forward.</p><img src="https://counter.theconversation.com/content/189841/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Omer Aijazi receives funding from the Social Sciences and Humanities Research Council of Canada (SSHRC) to conduct research on disaster recovery in Pakistan.</span></em></p>The culpability for Pakistan’s catastrophic floods rests with the government and wealthy polluter countries.Omer Aijazi, Visiting Researcher, University of VictoriaLicensed 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/1436262020-08-03T19:59:31Z2020-08-03T19:59:31ZHow climate change made the melting of New Zealand’s glaciers 10 times more likely<figure><img src="https://images.theconversation.com/files/350739/original/file-20200802-20-dzc6om.jpg?ixlib=rb-1.1.0&rect=37%2C142%2C6282%2C3809&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Dave Allen</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Glaciers around the world are melting — and for the first time, we can now directly attribute annual ice loss to climate change.</p>
<p>We analysed two years in which glaciers in New Zealand melted the most in at least four decades: 2011 and 2018. Both years were characterised by warmer than average temperatures of the air and the surface of the ocean, especially during summer. </p>
<p>Our <a href="https://www.nature.com/articles/s41558-020-0849-2">research</a>, published today, shows climate change made the glacial melt that happened during the summer of 2018 at least ten times more likely. </p>
<figure class="align-center ">
<img alt="A person taking an image of a glacier" src="https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/350809/original/file-20200803-16-dj1oid.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">Scientists have been monitoring glaciers in New Zealand for more than 40 years.</span>
<span class="attribution"><span class="source">Dave Allen</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>As the Earth continues to warm, we expect an even stronger human fingerprint on extreme glacier mass loss in the coming decades.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-birds-eye-view-of-new-zealands-changing-glaciers-97074">A bird’s eye view of New Zealand's changing glaciers</a>
</strong>
</em>
</p>
<hr>
<h2>Extreme glacier melt</h2>
<p>During the 2018 summer, the Tasman Sea marine heatwave resulted in the <a href="https://niwa.co.nz/climate/special-climate-statement-record-warmth-march-2018">warmest sea surface temperatures</a> around New Zealand on record — up to 2°C above average.</p>
<p>Research <a href="http://www.ametsoc.net/eee/2017a/ch20_EEEof2017_Perkins.pdf">shows</a> these record sea surface temperatures were almost certainly due to the influence of climate change.</p>
<figure class="align-center ">
<img alt="map of sea surface temperatures" src="https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=219&fit=crop&dpr=1 600w, https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=219&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=219&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=275&fit=crop&dpr=1 754w, https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=275&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/350769/original/file-20200803-16-r245pa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=275&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Summer sea surface temperature anomalies (in °C, relative to mean temperatures between 1979 and 2009) for December 2010 to February 2011 (left) and December 2017 to February 2018 (right),</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The results of our work show climate change made the high melt in 2011 at least six times more likely, and in 2018, it was at least ten times more likely.</p>
<p>These likelihoods are changing because global average temperatures, including in New Zealand, are now about 1°C above pre-industrial levels, confirming a connection between greenhouse gas emissions and high annual ice loss. </p>
<h2>Changing New Zealand glaciers</h2>
<figure class="align-right ">
<img alt="Glaciers in New Zealand's mountains" src="https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1130&fit=crop&dpr=1 754w, https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1130&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/350772/original/file-20200803-14-gri4lh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1130&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New Zealand’s glaciers lost more ice in 2011 and 2018 than in any other year in the last four decades.</span>
<span class="attribution"><span class="source">Dave Allen</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We use several methods to track changes in New Zealand glaciers. </p>
<p>First, the <a href="https://niwa.co.nz/climate/research-projects/climate-present-and-past/southern-alps-glaciers/end-of-summer-snowline-survey">end-of-summer snowline survey</a> began in 1977. It involves taking photographs of over 50 glaciers in the Southern Alps every March. </p>
<p>From these images, we calculate the snowline elevation (the lowest elevation of snow on the glacier) to determine the <a href="https://vimeo.com/405686001">glacier’s health</a>. The less snow there is left on a glacier at the end of summer, the more ice the glacier has lost.</p>
<p>The second method is our annual measurement of a glacier’s mass balance — the total gain or loss of ice from a glacier over a year. These measurements require trips to the glacier each year to measure snow accumulation, and snow and ice melt. Mass balance is measured for only two glaciers in the Southern Alps, Brewster Glacier (since 2005) and Rolleston Glacier (since 2010). </p>
<p>Both methods show New Zealand glaciers lost more ice in 2011 and 2018 than during earlier years since the start of the snowline surveys in 1977. </p>
<p><img src="https://cdn.theconversation.com/static_files/files/1149/brewster.gif?1596427463" width="100%"></p>
<p>Images taken during the end-of-summer snowline survey show how the amount of white snow at high elevations on Brewster Glacier decreases over time, compared to darker, bluer ice at lower elevations.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-long-term-environmental-observations-are-crucial-for-new-zealands-water-security-challenges-141123">Why long-term environmental observations are crucial for New Zealand's water security challenges</a>
</strong>
</em>
</p>
<hr>
<h2>Attributing extreme melt</h2>
<p>Earlier research has quantified the human influence on extreme climate events such as <a href="https://www.worldweatherattribution.org/wp-content/uploads/WWA-Science_France_heat_June_2019.pdf">heatwaves</a>, <a href="http://www.ametsoc.net/eee/2016/ch27.pdf">extreme rainfall</a> and <a href="https://journals.ametsoc.org/jcli/article/31/6/2465/89985">droughts</a>. We combined the established method of calculating the impact of climate change on extreme events with models of glacier mass balance. In this way, we could determine whether or not climate change has influenced extreme glacier melt.</p>
<p>This is the first study to attribute annual glacier melt to climate change, and only the second to directly <a href="https://science.sciencemag.org/content/sci/345/6199/919.full.pdf?casa_token=asEJJV92IW8AAAAA:cnlFxJnAr35ienpvFUUkik25QPqm_VBitK5G3YzvJTr-NEsKNBoj5FcRn4iW-wb6nVTlkFoDhk_ioNc">link glacier melt to climate change</a>. With multiple studies in agreement, we can be more confident there is a link between human activity and glacier melt. </p>
<figure>
<iframe src="https://player.vimeo.com/video/443262699" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Franz Josef is another iconic New Zealand glacier. This timelapse video shows it has retreated by 900 metres since 2012. Credit: Brian Anderson.</span></figcaption>
</figure>
<p>This confidence is especially important for Intergovernmental Panel on Climate Change (<a href="https://www.ipcc.ch/">IPCC</a>) reports, which use findings like ours to inform policymakers. </p>
<p>Recent <a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019EF001470">research</a> shows New Zealand glaciers will lose about 80% of area and volume between 2015 and the end of the century if greenhouse gas emissions continue to rise at current rates. Glaciers in New Zealand are important for tourism, alpine sports and as a water resource. </p>
<p>Glacial retreat is accelerating globally, especially in the past decade.
<a href="https://www.nature.com/articles/s41558-017-0049-x">Research</a> shows by 2090, the water runoff from glaciers will decrease by up to 10% in regions including central Asia and the Andes, raising major concerns over the sustainability of water resources where they are already limited.</p>
<p>The next step in our work is to calculate the influence of climate change on extreme melt for glaciers around the world. Ultimately, we hope this will contribute to evidence-based decisions on climate policy and convince people to take stronger action to curb climate change.</p><img src="https://counter.theconversation.com/content/143626/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lauren Vargo receives funding from a NIWA subcontract to VUW to undertake Structure From Motion work using the NIWA EOSS photo archive.</span></em></p>For the first time, scientists have been able to quantify how much climate change contributed to glacial melt, using more than 40 years of data from New Zealand’s retreating glaciers.Lauren Vargo, Research Fellow in the Antarctic Research Centre, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1411232020-06-23T20:16:36Z2020-06-23T20:16:36ZWhy long-term environmental observations are crucial for New Zealand’s water security challenges<figure><img src="https://images.theconversation.com/files/343086/original/file-20200622-75529-oz7678.jpg?ixlib=rb-1.1.0&rect=41%2C113%2C3947%2C1764&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Andrew Lorrey</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Brewster Glacier in New Zealand’s Southern Alps lost 13 million cubic metres of ice between March 2016 and March 2019 - almost the equivalent of the basic drinking water needs of all New Zealanders during that time. </p>
<figure>
<iframe src="https://player.vimeo.com/video/405686001" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
<figcaption><span class="caption">Climate and glacier scientists monitor New Zealand’s ice and snow. Video produced by Rebekah Parsons-King and Stuart MacKay.</span></figcaption>
</figure>
<p>Simultaneously, seasonal extremes for Auckland - New Zealand’s largest city - swung from the wettest autumn on record to one of the most severe multi-season droughts.</p>
<p>Water is arguably the most precious resource in New Zealand. These contrasting extreme events in two very different regions highlight the critical importance of long-term observations as we confront water security challenges.</p>
<h2>Water extremes</h2>
<p>2017 became the wettest autumn on record for Auckland when an “<a href="https://www.nature.com/articles/ngeo2894">atmospheric river</a>” drenched the city for several days. Within a month, ex-tropical cyclones <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/joc.3753">dumped even more extreme rainfall</a>. </p>
<p>Exceptionally high autumn rainfall (more than 200% higher than normal for many sites) during 2017 saturated soils and produced numerous slips. Sediment hampered water treatment for regional reservoirs that provide about 75% of the city’s water supply. </p>
<p>Fast forward to 2019, when one of the most significant multi-season droughts since the early 20th century started unfolding. Four Auckland sites we monitor show it was the driest summer in recent memory. The drought has continued, and <a href="https://www.stuff.co.nz/auckland/121614214/auckland-drought-little-sign-of-relief-for-declining-water-supply">water restrictions</a> are currently in place.</p>
<p>The big wet versus the big dry in Auckland only three years apart gives us a taste of New Zealand’s water future - a higher likelihood of <a href="https://knowledgeauckland.org.nz/media/1171/tr2017-031-2-auckland-region-climate-change-projections-and-impacts-summary-revised-jan-2018.pdf">more frequent water extremes with stronger impacts</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343083/original/file-20200622-75522-xjzrrm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The stark contrast between extreme wet and dry conditions for the North Island (top) had significantly different impacts on Upper Mangatawhiri Reservoir (bottom). Both led to water conservation calls in Auckland.</span>
<span class="attribution"><span class="source">Climate data and visualisation: NIWA ; Google Earth maps</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Shrinking ice</h2>
<p>The Southern Alps tell a different story arising from climate extremes, where recent changes have been rapid, widespread and exceptional. The National Institute of Water and Atmosphere <a href="https://niwa.co.nz/climate/research-projects/climate-present-and-past/southern-alps-glaciers/end-of-summer-snowline-survey">end-of-summer snowline mission</a> – which has run nearly unbroken since the 1970s – provides valuable “time capsules” of glaciers and snowlines through a changing climate. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-birds-eye-view-of-new-zealands-changing-glaciers-97074">A bird’s eye view of New Zealand's changing glaciers</a>
</strong>
</em>
</p>
<hr>
<p>The long-term permanent snowline – the boundary between exposed glacial ice and recent snow – must sit below the mountain top for a glacier to exist. The 2018 Tasman Sea <a href="https://niwa.co.nz/climate/special-climate-statement-record-warmth-march-2018">marine heatwave</a> drove snowlines off the top of many peaks. Then, 2019 produced a second marine heatwave around northern New Zealand. Some small glaciers sustained so much damage during these extreme years that they are now on a path to extinction. </p>
<p>As if this wasn’t enough, <a href="https://www.theguardian.com/world/2020/jan/02/new-zealand-glaciers-turn-brown-from-australian-bushfires-smoke-ash-and-dust">ash and dust from Australian bushfires</a> blanketed Southern Alps glaciers during the 2020 summer and increased the potential for seasonal melt. </p>
<p>New <a href="https://www.nature.com/articles/s43017-020-0023-4">photogrammetry techniques</a> that produce digital elevation models with annual glacier photos help to define the impacts from extreme years like the last three. We are extending these techniques to our historic image archive to construct a 4D vision of ice volume, which brings us closer to quantifying water volume loss and gain for individual glaciers. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=326&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=326&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=326&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=410&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=410&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343085/original/file-20200622-75487-jipfd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=410&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Rising temperatures, higher snowlines, glacial lake expansion and dust from Australian bushfires are pushing some South Island glaciers towards extinction.</span>
<span class="attribution"><span class="source">Andrew Lorrey</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The recent ice loss from Brewster Glacier is only a small part of the frozen water volume stored in New Zealand’s Southern Alps. Since the first New Zealand glacier survey in the late 1970s, there’s been a long-term trend of glacial retreat through climate warming. </p>
<p>Southern Alps glaciers are estimated to <a href="https://theconversation.com/new-zealands-southern-alps-have-lost-a-third-of-their-ice-28916">have lost more than 30%</a> of their volume - about 16 billion cubic metres of ice, or the equivalent of about 200 litres a day for each New Zealander over 40 years. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-zealands-southern-alps-have-lost-a-third-of-their-ice-28916">New Zealand’s Southern Alps have lost a third of their ice</a>
</strong>
</em>
</p>
<hr>
<p>While water loss from vanishing glaciers is deeply troubling, it is a reminder that more severe and immediate concerns can arise from long and intense seasonal droughts and changes to <a href="https://www.mfe.govt.nz/sites/default/files/media/Climate%20Change/Hydrological%20projections%20report-final.pdf">rivers in a warming world</a>.</p>
<h2>Past and present observations help prepare for the future</h2>
<p>Long-term environmental observations help to inform national water security policy and water resource management. Our observations also underpin weather forecasts, <a href="https://niwa.co.nz/climate/seasonal-climate-outlook">seasonal climate predictions</a> and <a href="https://www.mfe.govt.nz/publications/climate-change/climate-change-projections-new-zealand">climate change projections</a> that cover a spectrum of advance warnings for extreme weather and climate impacts. </p>
<p>We need to grow environmental observations, but making and archiving them can be costly and difficult. Global support for their long-term stewardship once they are gathered is also at risk. As a result, small countries like New Zealand confront hard choices about which observations to make, what sites they come from, and how they are continued. </p>
<p>Amid the many COVID-19 announcements was an increase in funding for <a href="https://www.mbie.govt.nz/science-and-technology/science-and-innovation/agencies-policies-and-budget-initiatives/budget-initiatives/">nationally significant databases and collections</a>. This boost is a welcome signal for maintaining valuable scientific resources, including environmental observations, for future generations. </p>
<p>But ongoing support is needed to reduce attrition of our comprehensive evidence base. It would be even more risky to abandon long-term water and climate observations, and simply fly blind into an uncertain future.</p><img src="https://counter.theconversation.com/content/141123/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>AL receives financial support from NIWA for climate research and forecasting.
Rebekah Parsons-King and Stuart MacKay produced the video “Glaciers: A time capsule” with some support from the NIWA core-funded project “Climate Present and Past” (Contract CAOA2001) that AL leads.
</span></em></p><p class="fine-print"><em><span>BN receives financial support from NIWA for climate research and forecasting.</span></em></p><p class="fine-print"><em><span>LV receives financial support from a NIWA subcontract to VUW to undertake Structure From Motion work using the NIWA EOSS photo archive.</span></em></p>Auckland’s extreme drought and the rapid retreat of glaciers in the Southern Alps both highlight how important long-term observations are for water management policy and planning.Andrew Lorrey, Principal Scientist & Programme Leader of Climate Observations and Processes, National Institute of Water and Atmospheric ResearchBen Noll, Meteorologist/forecaster, National Institute of Water and Atmospheric ResearchLauren Vargo, Research Fellow in the Antarctic Research Centre, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1218642019-08-14T20:01:06Z2019-08-14T20:01:06ZNew research shows that Antarctica’s largest floating ice shelf is highly sensitive to warming of the ocean<figure><img src="https://images.theconversation.com/files/287935/original/file-20190813-9442-wsmk2i.jpg?ixlib=rb-1.1.0&rect=32%2C124%2C4338%2C2785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Since the last ice age, the ice sheet retreated over a thousand kilometres in the Ross Sea region, more than any other region on the continent.</span> <span class="attribution"><span class="source">Rich Jones</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Scientists have long been concerned about the <a href="https://www.nature.com/articles/271321a0">potential collapse of the West Antarctic Ice Sheet</a> and its contribution to global sea level rise. Much of West Antarctica’s ice lies below sea level, and warming ocean temperatures may lead to runaway ice sheet retreat. </p>
<p>This process, called marine ice sheet instability, has already been observed along parts of the Amundsen Sea region, where <a href="https://science.sciencemag.org/content/341/6143/266">warming of the ocean has led to melting underneath the floating ice shelves</a> that fringe the continent. As these ice shelves thin, the ice grounded on land flows more rapidly into the ocean and raises the sea level.</p>
<p>Although the Amundsen Sea region has shown the most rapid changes to date, more ice actually <a href="https://science.sciencemag.org/content/333/6048/1427">drains from West Antarctica via the Ross Ice Shelf</a> than any other area. How this ice sheet responds to climate change in the Ross Sea region is therefore a key factor in Antarctica’s contribution to global sea level rise in the future.</p>
<p>Periods of past ice sheet retreat can give us insights into how sensitive the Ross Sea region is to changes in ocean and air temperatures. Our <a href="https://advances.sciencemag.org/content/5/8/eaav8754">research</a>, published today, argues that ocean warming was a key driver of glacial retreat since the last ice age in the Ross Sea. This suggests that the Ross Ice Shelf is highly sensitive to changes in the ocean.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ice-melt-in-greenland-and-antarctica-predicted-to-bring-more-frequent-extreme-weather-111082">Ice melt in Greenland and Antarctica predicted to bring more frequent extreme weather</a>
</strong>
</em>
</p>
<hr>
<h2>History of the Ross Sea</h2>
<p>Since the last ice age, the ice sheet <a href="https://www.sciencedirect.com/science/article/pii/S0277379113003338">retreated more than 1,000km in the Ross Sea region</a> – more than any other region on the continent. But there is little consensus among the scientific community about how much climate and the ocean have contributed to this retreat. </p>
<p>Much of what we know about the past ice sheet retreat in the Ross Sea comes from rock samples found in the Transantarctic Mountains. Dating techniques allow scientists to determine when these rocks were exposed to the surface as the ice around them retreated. These rock samples, which were collected far from where the initial ice retreat took place, have generally led to <a href="https://science.sciencemag.org/content/286/5438/280">interpretations</a> in which the ice sheet retreat happened much later than, and independently of, the rise in air and ocean temperatures following the last ice age.</p>
<p>But <a href="https://www.nature.com/articles/s41598-018-29911-8">radiocarbon ages from sediments</a> in the Ross Sea suggest an earlier retreat, more in line with when climate began to warm from the last ice age. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287937/original/file-20190813-9409-pjv0by.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">An iceberg floating in the Ross Sea - an area that is sensitive to warming in the ocean.</span>
<span class="attribution"><span class="source">Rich Jones</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Using models to understand the past</h2>
<p>To investigate how sensitive this region was to past changes, we developed a regional model of the Antarctic ice sheet. The model works by simulating the physics of the ice sheet and its response to changes in ocean and air temperatures. The simulations are then compared to geological records to check accuracy.</p>
<p>Our main findings are that warming of the ocean and atmosphere were the main causes of the major glacial retreat that took place in the Ross Sea region since the last ice age. But the dominance of these two controls in influencing the ice sheet evolved through time. Although air temperatures influenced the timing of the initial ice sheet retreat, ocean warming became the main driver due to melting of the Ross Ice Shelf from below, similar to what is currently observed in the Amundsen Sea. </p>
<p>The model also identifies key areas of uncertainty of past ice sheet behaviour. Obtaining sediment and rock samples and oceanographic data would help to improve modelling capabilities. The <a href="https://science.sciencemag.org/content/333/6048/1427">Siple Coast region of the Ross Ice Shelf is especially sensitive to changes</a> in melt rates at the base of the ice shelf, and is therefore a critical region to sample.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-scientists-explore-hidden-ocean-beneath-antarcticas-largest-ice-shelf-90006">Climate scientists explore hidden ocean beneath Antarctica's largest ice shelf</a>
</strong>
</em>
</p>
<hr>
<h2>Implications for the future</h2>
<p>Understanding processes that were important in the past allows us to improve and validate our model, which in turn gives us confidence in our future projections. Through its history, the ice sheet in the Ross Sea has been sensitive to changes in ocean and air temperatures. Currently, ocean warming underneath the Ross Ice Shelf is the main concern, given its potential to cause melting from below. </p>
<p>Challenges remain in determining exactly how ocean temperatures will change underneath the Ross Ice Shelf in the coming decades. This will depend on changes to patterns of ocean circulation, with complex interactions and feedback between sea ice, surface winds and <a href="https://www.nature.com/articles/s41586-019-0889-9">melt water from the ice sheet</a>. </p>
<p>Given the sensitivity of ice shelves to ocean warming, we need an integrated modelling approach that can accurately reproduce both the ocean circulation and dynamics of the ice sheet. But the computational cost is high. </p>
<p>Ultimately, these integrated projections of the Southern Ocean and Antarctic ice sheet will help policymakers and communities to develop meaningful adaptation strategies for cities and coastal infrastructure exposed to the risk of rising seas.</p><img src="https://counter.theconversation.com/content/121864/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Lowry's PhD work is funded from the Royal Society Te Aparangi Marsden Fund through Victoria University of Wellington and the Antarctica New Zealand Doctoral Scholarship program.</span></em></p>New research shows that ocean and air temperatures both contributed to the melting of Antarctica’s Ross Ice Shelf in the past, but melting from below by a warming ocean became more important over time.Dan Lowry, PhD candidate, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.