Ashley, Kate E. , McKay, Robert , Etourneau, Johan, Jimenez-Espejo, Francisco J., Condron, Alan , Albot, Anna, Crosta, Xavier, Riesselman, Christina , Seki, Osamu, Massé, Guillaume, Golledge, Nicholas R. , Gasson, Edward, Lowry, Daniel P. , Barrand, Nicholas E. , Johnson, Katelyn , Bertler, Nancy , Escutia, Carlota, Dunbar, Robert and Bendle, James A. (2021) Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat. Climate of the Past, 17 (1). pp. 1-19. DOI 10.5194/cp-17-1-2021.

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Abstract

Over recent decades Antarctic sea-ice extent has increased, alongside widespread ice shelf thinning and freshening of waters along the Antarctic margin. In contrast, Earth system models generally simulate a decrease in sea ice. Circulation of water masses beneath large-cavity ice shelves is not included in current Earth System models and may be a driver of this phenomena. We examine a Holocene sediment core off East Antarctica that records the Neoglacial transition, the last major baseline shift of Antarctic sea ice, and part of a late-Holocene global cooling trend. We provide a multi-proxy record of Holocene glacial meltwater input, sediment transport, and sea-ice variability. Our record, supported by high-resolution ocean modelling, shows that a rapid Antarctic sea-ice increase during the mid-Holocene (∼ 4.5 ka) occurred against a backdrop of increasing glacial meltwater input and gradual climate warming. We suggest that mid-Holocene ice shelf cavity expansion led to cooling of surface waters and sea-ice growth that slowed basal ice shelf melting. Incorporating this feedback mechanism into global climate models will be important for future projections of Antarctic changes.

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