Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation

<p>We report cosmogenic-nuclide measurements from two isolated groups of nunataks in West Antarctica: the Pirrit Hills, located midway between the grounding line and the divide in the Weddell Sea sector, and the Whitmore Mountains, located along the Ross–Weddell divide. At the Pirrit Hills, ev...

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Bibliographic Details
Main Authors:	P. Spector, J. Stone, B. Goehring
Format:	Article
Language:	English
Published:	Copernicus Publications 2019-11-01
Series:	The Cryosphere
Online Access:	https://www.the-cryosphere.net/13/3061/2019/tc-13-3061-2019.pdf

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spelling	doaj-44c6aaa1b1b748f6adbdcc986aea99972020-11-25T01:11:45ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242019-11-01133061307510.5194/tc-13-3061-2019Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciationP. Spector0J. Stone1B. Goehring2Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA, USADepartment of Earth and Space Sciences, University of Washington, Seattle, WA, USADepartment of Earth and Environmental Sciences, Tulane University, New Orleans, LA, USA<p>We report cosmogenic-nuclide measurements from two isolated groups of nunataks in West Antarctica: the Pirrit Hills, located midway between the grounding line and the divide in the Weddell Sea sector, and the Whitmore Mountains, located along the Ross–Weddell divide. At the Pirrit Hills, evidence of glacial-stage ice cover extends <span class="inline-formula">∼320</span> m above the present ice surface. Subsequent thinning mostly occurred after <span class="inline-formula">∼14</span> kyr BP, and modern ice levels were established some time after <span class="inline-formula">∼4</span> kyr BP. We infer that, like at other flank sites, these changes were primarily controlled by the position of the grounding line downstream. At the Whitmore Mountains, cosmogenic <span class="inline-formula"><sup>14</sup>C</span> concentrations in bedrock surfaces demonstrate that ice there was no more than <span class="inline-formula">∼190</span> m thicker than present during the past <span class="inline-formula">∼30</span> kyr. Combined with other constraints from West Antarctica, the <span class="inline-formula"><sup>14</sup>C</span> data imply that the divide was thicker than present for a period of less than <span class="inline-formula">∼8</span> kyr within the past <span class="inline-formula">∼15</span> kyr. These results are consistent with the hypothesis that the divide initially thickened due to the deglacial rise in snowfall and subsequently thinned in response to retreat of the ice-sheet margin. We use these data to evaluate several recently published ice-sheet models at the Pirrit Hills and Whitmore Mountains. Most of the models we consider do not match the observed timing and/or magnitude of thickness change at these sites. However, one model performs relatively well at both sites, which may, in part, be due to the fact that it was calibrated with geological observations of ice-thickness change from other sites in Antarctica.</p>https://www.the-cryosphere.net/13/3061/2019/tc-13-3061-2019.pdf
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	P. Spector J. Stone B. Goehring
spellingShingle	P. Spector J. Stone B. Goehring Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation The Cryosphere
author_facet	P. Spector J. Stone B. Goehring
author_sort	P. Spector
title	Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation
title_short	Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation
title_full	Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation
title_fullStr	Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation
title_full_unstemmed	Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation
title_sort	thickness of the divide and flank of the west antarctic ice sheet through the last deglaciation
publisher	Copernicus Publications
series	The Cryosphere
issn	1994-0416 1994-0424
publishDate	2019-11-01
description	<p>We report cosmogenic-nuclide measurements from two isolated groups of nunataks in West Antarctica: the Pirrit Hills, located midway between the grounding line and the divide in the Weddell Sea sector, and the Whitmore Mountains, located along the Ross–Weddell divide. At the Pirrit Hills, evidence of glacial-stage ice cover extends <span class="inline-formula">∼320</span> m above the present ice surface. Subsequent thinning mostly occurred after <span class="inline-formula">∼14</span> kyr BP, and modern ice levels were established some time after <span class="inline-formula">∼4</span> kyr BP. We infer that, like at other flank sites, these changes were primarily controlled by the position of the grounding line downstream. At the Whitmore Mountains, cosmogenic <span class="inline-formula"><sup>14</sup>C</span> concentrations in bedrock surfaces demonstrate that ice there was no more than <span class="inline-formula">∼190</span> m thicker than present during the past <span class="inline-formula">∼30</span> kyr. Combined with other constraints from West Antarctica, the <span class="inline-formula"><sup>14</sup>C</span> data imply that the divide was thicker than present for a period of less than <span class="inline-formula">∼8</span> kyr within the past <span class="inline-formula">∼15</span> kyr. These results are consistent with the hypothesis that the divide initially thickened due to the deglacial rise in snowfall and subsequently thinned in response to retreat of the ice-sheet margin. We use these data to evaluate several recently published ice-sheet models at the Pirrit Hills and Whitmore Mountains. Most of the models we consider do not match the observed timing and/or magnitude of thickness change at these sites. However, one model performs relatively well at both sites, which may, in part, be due to the fact that it was calibrated with geological observations of ice-thickness change from other sites in Antarctica.</p>
url	https://www.the-cryosphere.net/13/3061/2019/tc-13-3061-2019.pdf
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Thickness of the divide and flank of the West Antarctic Ice Sheet through the last deglaciation

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