Antarctic sea ice over the past 130 000 years – Part 1: a review of what proxy records tell us

• Published in: Climate of the Past
• Main Authors: Crosta, Xavier, Kohfeld, Karen E., Bostock, Helen C., Chadwick, Matthew, Vivier, Alice, Esper, Oliver, Etourneau, Johan, Jones, Jacob, Leventer, Amy, Müller, Juliane, Rhodes, Rachael H., Allen, Claire S., Ghadi, Pooja, Lamping, Nele, Lange, Carina B., Lawler, Kelly-Anne, Lund, David, Marzocchi, Alice, Meissner, Katrin J., Menviel, Laurie, Nair, Abhilash, Patterson, Molly, Pike, Jennifer, Prebble, Joseph G., Riesselman, Christina, Sadatzki, Henrik, Sime, Louise C., Shukla, Sunil K., Thöle, Lena, Vorrath, Maria-Elena, Xiao, Wenshen, Yang, Jiao
• Format: Text
• Language: English
• Published: 2022
• Subjects: Antarctic; Weddell; Antarc*; Antarctica; ice core; Ice Shelf; Sea ice
• Online Access: https://doi.org/10.5194/cp-18-1729-2022; https://cp.copernicus.org/articles/18/1729/2022/

Antarctic sea ice plays a critical role in the Earth system, influencing energy, heat and freshwater fluxes, air–sea gas exchange, ice shelf dynamics, ocean circulation, nutrient cycling, marine productivity and global carbon cycling. However, accurate simulation of recent sea-ice changes remains challenging and, therefore, projecting future sea-ice changes and their influence on the global climate system is uncertain. Reconstructing past changes in sea-ice cover can provide additional insights into climate feedbacks within the Earth system at different timescales. This paper is the first of two review papers from the Cycles of Sea Ice Dynamics in the Earth system (C-SIDE) working group. In this first paper, we review marine- and ice core-based sea-ice proxies and reconstructions of sea-ice changes throughout the last glacial–interglacial cycle. Antarctic sea-ice reconstructions rely mainly on diatom fossil assemblages and highly branched isoprenoid (HBI) alkenes in marine sediments, supported by chemical proxies in Antarctic ice cores. Most reconstructions for the Last Glacial Maximum (LGM) suggest that winter sea ice expanded all around Antarctica and covered almost twice its modern surface extent. In contrast, LGM summer sea ice expanded mainly in the regions off the Weddell and Ross seas. The difference between winter and summer sea ice during the LGM led to a larger seasonal cycle than today. More recent efforts have focused on reconstructing Antarctic sea ice during warm periods, such as the Holocene and the Last Interglacial (LIG), which may serve as an analogue for the future. Notwithstanding regional heterogeneities, existing reconstructions suggest that sea-ice cover increased from the warm mid-Holocene to the colder Late Holocene with pervasive decadal- to millennial-scale variability throughout the Holocene. Studies, supported by proxy modelling experiments, suggest that sea-ice cover was halved during the warmer LIG when global average temperatures were ∼2 ∘ C above the pre-industrial (PI). There ...