Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat

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; Bendle, James A.

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 (inline-formula∼ 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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Ashley, Kate E. / McKay, Robert / Etourneau, Johan / et al: Mid-Holocene Antarctic sea-ice increase driven by marine ice sheet retreat. 2021. Copernicus Publications.

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