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Abstract

The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (∼2 m), ocean thermal expansion, and melting mountain glaciers (∼1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic meridional overturning circulation in response to North Atlantic surface freshening. Here, we report a blue-ice record of ice sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS), which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide evidence for substantial mass loss across the Weddell Sea Embayment during the LIG, most likely driven by ocean warming and associated with destabilization of subglacial hydrates. Ice sheet modeling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multimeter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice–climate feedbacks that further amplify warming.

Item Type:	Article
Authors/Creators:	Turney, CSM and Fogwill, CJ and Golledge, NR and McKay, NP and van Sebille, E and Jones, RT and Etheridge, D and Rubino, M and Thornton, DP and Davies, SM and Ramsey, CB and Thomas, ZA and Bird, MI and Munksgard, NC and Kohno, M and Woodward, J and Winter, K and Weyrich, LS and Rootes, CM and Millman, H and Albert, PG and Rivera, A and van Ommen, T and Curran, M and Moy, A and Rahmstorf, S and Kawamura, K and Hillenbrand, C-D and Weber, ME and Manning, CJ and Young, J and Cooper, A
Keywords:	Antarctic ice sheets, marine ice sheet instability (MISI), paleoclimatology, polar amplification, tipping element
Journal or Publication Title:	Proceedings of the National Academy of Sciences of The United States of America
Publisher:	Natl Acad Sciences
ISSN:	0027-8424
DOI / ID Number:	https://doi.org/10.1073/pnas.1902469117
Copyright Information:	Copyright 2020 The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/
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