[M-IS03] The Southern Ocean and the Antarctic Ice Sheet dynamics in past, present and future

[MIS03-P01] Reconstruction of surface and deep water environments in the Indian sector of the Southern Ocean during MIS 11

*Hiroki Matsui¹, Isabelle Billy², Olivier Ther², Xavier Crosta², Minoru Ikehara³ (1.Graduate School of International Resource Sciences, Akita University, 2.University of Bordeaux, France, 3.Center for Advanced Marine Core Research, Kochi University)

Keywords:MIS 11, Oceanic front, Foraminifera

During Marine Isotope Stage (MIS) 11, the interglacial period around 400 kyrs ago, global average temperature possibly reached to 2°C warmer than preindustrial. Because MIS 11 is a potential analogue for future climate, understanding response of Southern Ocean (SO) during MIS 11 is important. In this study, we reconstruct surface and deep water environments in the SO during MIS 11, based on foraminifera assemblages from two marine-sediment core in the Indian sector of the SO. The MD19-3576 core is located north of the modern Subantarctic Front, whereas the MD19-3578 core is located south of the front.
For the MD19-3576 core, planktic foraminifera Neogloboquadrina pachyderma yielded at least 9% during MIS 11. Relative abundance of N. pachyderma can be converted to summer sea surface temperature (SSST), based on surface sediments dataset, and ~9% corresponds to ~10.6°C. Coretop SSST at the MD19-3576 core is ~9.7°C, which is comparable to ~10.6°C during MIS 11 considering the uncertainty of the SSST reconstruction. In contrast, N. pachydrma presented at least 22% for the MD19-3578 core during MIS 11, which corresponds to ~9.4°C. Coretop SSST at the MD19-3578 core is ~6.3°C, indicating SSST during MIS 11 is significantly high. We suggest that the Subantarctic Front migrated southward than today, and two cores studied were located north of the front. In the presentation, benthic foraminiferal assemblages are also reported, to discuss surface and deep water environments in the SO during MIS 11.