Reconstructing Antarctic winter sea-ice extent during Marine Isotope Stage 5e

Marine Isotope Stage (MIS) 5e marks the peak of the last interglacial (130-116 ka) and is an important ‘process analogue’ for understanding the high latitude climatic feedbacks and forcings active under future anthropogenic warming. Antarctic sea-ice extent is a critical component of the Earth’s climate system through its impact on global albedo and its roles in Southern Hemisphere atmospheric and ocean circulation. Published marine sediment core records are located too far north to accurately constrain the timing and extent of the winter sea-ice (WSI) minimum during MIS 5e (Chadwick et al., 2020) and researchers/models have therefore assumed that this minimum occurs synchronously with the Antarctic peak warming in ice core records (Holloway et al., 2017).

This study presents new reconstructions of Southern Ocean WSI extent for MIS 5e based on the diatom species assemblage records in marine sediment cores. These records have robust age models, which allow for the different timings and patterns of WSI retreat throughout the Southern Ocean to be examined. In particular, the difference between the relatively stable WSI extent in the Pacific sector of the Southern Ocean and the more dynamic WSI extent in the Atlantic sector of the Southern Ocean. Using sediment cores located south of 55 ^oS creates a novel synthesis for assessing the evidence for the considerable MIS 5e WSI reduction (67% in the Atlantic sector) predicted by model simulations (Holloway et al., 2017).

References

Chadwick M., Allen C.S., Sime L.C., Hillenbrand C-D. (2020). Analysing the timing of peak warming and minimum winter sea-ice extent in the Southern Ocean during MIS 5e. Quaternary Science Reviews, 229: 106134.

Holloway M.D., Sime L.C., Allen C.S., Hillenbrand C-D., Bunch P., Wolff E., Valdes P.J. (2017). The Spatial Structure of the 128 ka Antarctic Sea Ice Minimum. Geophysical Research Letters, 44 (21): 11129-11139.