New constraints on the timing of West Antarctic ice sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum

Smith, James A. ORCID: https://orcid.org/0000-0002-1333-2544; Hillenbrand, Claus-Dieter ORCID: https://orcid.org/0000-0003-0240-7317; Kuhn, Gerard; Klages, Johann Phillip; Graham, Alastair C.G.; Larter, Robert D. ORCID: https://orcid.org/0000-0002-8414-7389; Ehrmann, Werner; Moreton, Steven G.; Wiers, Steffen. 2014 New constraints on the timing of West Antarctic ice sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum. Global and Planetary Change, 122. 224-237. 10.1016/j.gloplacha.2014.07.015

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Abstract/Summary

Glaciers flowing into the Amundsen Sea Embayment (ASE) account for > 35% of the total discharge of the West Antarctic Ice Sheet (WAIS) and have thinned and retreated dramatically over the past two decades. Here we present detailed marine geological data and an extensive new radiocarbon dataset from the eastern ASE in order to constrain the retreat of the WAIS since the Last Glacial Maximum (LGM) and assess the significance of these recent changes. Our dating approach, relying mainly on the acid insoluble organic (AIO) fraction, utilises multi-proxy analyses of the sediments to characterise their lithofacies and determine the horizon in each core that would yield the most reliable age for deglaciation. In total, we dated 69 samples and show that deglaciation of the outer shelf was underway before 20,600 calibrated years before present (cal yr BP), reaching the mid-shelf by 13,575 cal yr BP and the inner shelf to within ca. 150 km of the present grounding line by 10,615 cal yr BP. The timing of retreat is broadly consistent with previously published radiocarbon dates on biogenic carbonate from the eastern ASE as well as AIO 14C ages from the western ASE and provides new constraints for ice sheet models. The overall retreat trajectory – slow on the outer shelf, more rapid from the middle to inner shelf – clearly highlights the importance of reverse bedslopes in controlling phases of accelerated groundling line retreat. Despite revealing these broad scale trends, the current dataset does not capture detailed changes in ice flow, such as stillstands during grounding line retreat (i.e., deposition of grounding zone wedges) and possible readvances as depicted in the geomorphological record.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.gloplacha.2014.07.015
Programmes:	BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ice Sheets
Date made live:	19 Aug 2014 11:12 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/506994

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.gloplacha.2014.07.015

Programmes:

BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ice Sheets

Date made live:

19 Aug 2014 11:12 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/506994