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  • 1
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    Modelling West Antarctic ice sheet growth and collapse through the past five million years (2009)
    Nature Publishing Group (NPG)
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    Publication Date: 2009-03-20
    Description: The West Antarctic ice sheet (WAIS), with ice volume equivalent to approximately 5 m of sea level, has long been considered capable of past and future catastrophic collapse. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around approximately 15 kyr ago before retreating to near-modern locations by approximately 3 kyr ago. Prior collapses during the warmth of the early Pliocene epoch and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments. Until now, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at marine isotope stage 31 ( approximately 1.07 Myr ago) and other super-interglacials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pollard, David -- DeConto, Robert M -- England -- Nature. 2009 Mar 19;458(7236):329-32. doi: 10.1038/nature07809.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA. pollard@essc.psu.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19295608" target="_blank"〉PubMed〈/a〉
    Keywords: Antarctic Regions ; Diatoms ; History, Ancient ; *Ice Cover ; *Models, Theoretical ; Oceans and Seas ; Oxygen Isotopes ; Seawater ; Snow ; Time Factors
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    2.8 million years of Arctic climate change from Lake El'gygytgyn, NE Russia (2012)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2012-06-23
    Description: The reliability of Arctic climate predictions is currently hampered by insufficient knowledge of natural climate variability in the past. A sediment core from Lake El'gygytgyn in northeastern (NE) Russia provides a continuous, high-resolution record from the Arctic, spanning the past 2.8 million years. This core reveals numerous "super interglacials" during the Quaternary; for marine benthic isotope stages (MIS) 11c and 31, maximum summer temperatures and annual precipitation values are ~4 degrees to 5 degrees C and ~300 millimeters higher than those of MIS 1 and 5e. Climate simulations show that these extreme warm conditions are difficult to explain with greenhouse gas and astronomical forcing alone, implying the importance of amplifying feedbacks and far field influences. The timing of Arctic warming relative to West Antarctic Ice Sheet retreats implies strong interhemispheric climate connectivity.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Melles, Martin -- Brigham-Grette, Julie -- Minyuk, Pavel S -- Nowaczyk, Norbert R -- Wennrich, Volker -- DeConto, Robert M -- Anderson, Patricia M -- Andreev, Andrei A -- Coletti, Anthony -- Cook, Timothy L -- Haltia-Hovi, Eeva -- Kukkonen, Maaret -- Lozhkin, Anatoli V -- Rosen, Peter -- Tarasov, Pavel -- Vogel, Hendrik -- Wagner, Bernd -- New York, N.Y. -- Science. 2012 Jul 20;337(6092):315-20. doi: 10.1126/science.1222135. Epub 2012 Jun 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Geology and Mineralogy, University of Cologne, Zuelpicher Strasse 49a, D-50674 Cologne, Germany. mmelles@uni-koeln.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722254" target="_blank"〉PubMed〈/a〉
    Keywords: Arctic Regions ; *Climate Change ; *Cold Climate ; Geologic Sediments ; Ice Cover ; *Lakes ; Radiometric Dating ; Russia ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Contribution of Antarctica to past and future sea-level rise (2016)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2016-04-01
    Description: Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6-9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics-including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs-that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉DeConto, Robert M -- Pollard, David -- England -- Nature. 2016 Mar 31;531(7596):591-7. doi: 10.1038/nature17145.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA. ; Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27029274" target="_blank"〉PubMed〈/a〉
    Keywords: Antarctic Regions ; Atmosphere ; Calibration ; Climate Change/*statistics & numerical data ; Greenhouse Effect/statistics & numerical data ; *Ice Cover ; *Models, Theoretical ; Seawater/*analysis ; Temperature ; Time Factors ; Water Movements
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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