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

• Published in: Climate of the Past
• Main Authors: 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.
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; East Antarctica; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Ice Shelves; Sea ice
• Online Access: https://doi.org/10.5194/cp-17-1-2021; https://cp.copernicus.org/articles/17/1/2021/

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.