[M-IS15] Global Antarctic Science: connecting the chain of changing huge ice sheets and global environments

[MIS15-14] The southward shift of the Antarctic Polar Front and the westerlies during the last interglacial (MIS 5e) and their impact on the climate system

*Minoru Ikehara¹, Matthieu Civel-Mazens², Xavier Crosta³, Hiroki Matsui⁴ (1.Marine Core Research Institute, Kochi University, 2.LEMAR (UBO, CNRS, IRD, Ifremer), 3.University of Bordeaux, 4.Akita University)

Keywords:Southern Ocean, last interglacial, Antarctic Polar Front, westerlies

The Marine Isotope Stage (MIS) 5e, the peak of the last interglacial period, is one of the analogues of the future warming of Earth. The recent analysis of several sediment cores of the Indian sector of the Southern Ocean highlighted key differences between the ongoing and the last interglacial. Here, we compile the recent results obtained by our group and discuss the Indian Southern Ocean dynamics during MIS 5e and their link to global climate. Marine cores covering MIS 5e were mainly recovered in Del Caño Rise, Crozet Plateau, Kerguelen Plateau, and the Enderby Basin regions. Sea surface temperatures based on diatom assemblages were approximately 2°C higher during MIS 5e than in the present day, and subsurface water temperatures based on radiolarian assemblages also tended to be about 1°C higher. Combined to changes in planktic microfossil assemblages, these data suggest that the Antarctic Circumpolar Current and associated Antarctic and sub-Antarctic fronts shifted south during MIS 5e relative to its modern position. In particular, it is believed that the Antarctic Polar Front shifted about 5 degrees south of its present latitude and that it extended south of the Conrad Rise and as far as the Fawn Trough on the Kerguelen Plateau, a topographic constraint for the oceanic front. The increase in ocean temperature and the southward migration of the front zone during the last interglacial period was accompanied by a southward movement of the westerly wind belt and a reduction of the winter sea-ice extent. These processes are thought to have amplified the ocean-atmosphere feedback, essentially the outgassing of CO₂ through physical and biogeochemical feedbacks, further promoting global warming and affecting the global thermohaline circulation. They have also contributed to increase basal melting of the Antarctic ice shelf and affected global sea levels. These data set a natural basis for future Southern Ocean climate, as the same phenomena are already ongoing today.