[M-IS05] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS05-07] Abrupt Holocene ice-sheet retreat in Lutzow-Holm Bay, East Antarctica

*Yusuke Suganuma^1,2, Yuki Haneda³, Takuya Itaki³, Osamu Seki⁴, Takeshige Ishiwa¹, Moto Kawamata², Masakazu Fujii^1,2, Kazuya Kusahara⁸, Daisuke Hirano⁴, Masao Iwai⁹, Yuji Kato⁹, Hiroki Matsui⁶, Atsuko Amano³, Kota Katsuki⁵, Takayuki Omori⁷, Motohiro Hirabayashi¹, Hiroyuki Matsuzaki⁷, Takeyasu Yamagata⁷, Masato Ito⁸, Shin Sugiyama⁴, Naohisa Nishida¹⁰, Jun'ichi Okuno^1,2, Minoru Ikehara⁹, Hideki Miura^1,2 (1.National institute of Polar Research, 2.The Graduate University for Advanced Studies (SOKENDAI), 3.Geological Survey of Japan, AIST, 4.Hokkaido University, 5.Shimane University, 6.Akita University, 7.University of Tokyo, 8.JAMSTEC, 9.Center for Advanced Marine Core Research, Kochi University, 10.Tokyo Gakugei University)

Keywords:Antarctica Ice Sheet and Southern Ocean, Giant Reservoirs - Antarctic, Solid Earth

The Antarctic Ice Sheet (AIS) is one of the most significant potential contributors to future sea-level changes. Recently, the acceleration of AIS’s mass loss has been reported based on satellite observations, such as radar altimetry, interferometer, and gravity measurements, and shipboard observations coupled with modeling studies. In these studies, the main cause of the modern ice mass loss is thought to be iceberg calving and basal melting due to an inflow of modified Circumpolar Deep Water (mCDW). However, the role of the mCDW for the large-scale deglaciation of the AIS, such as the deglaciation since the Last Glacial Maximum (LGM), remains unclear due to the lack of the geological data-based constraint. Therefore, marine and land-based reconstruction of the deglaciation process of the AIS since the LGM is essential to understand the role of the mCDW for a large-scale ice mass loss, which will be a useful analog to calibrate the climate and ice sheet models and to refine the future ice sheet retreat projection. In this presentation, we show an overview of our recent activities in the Lützow-Holm Bay (LHB), Dronning Maud Land, East Antarctica. Newly obtained sedimentary cores and legacy samples from the LHB are used for detailed lithofacies analysis, authigenic Be-10 measurement, hydrogen isotopic compositions analysis, and benthic foraminiferal assemblage of the sedimentary cores. And also, a hybrid age model is constructed by foraminiferal and calibrated bulk organic carbon AMS C-14 dates. These indicate that the East AIS rapidly retreated since the Early Holocene due to an intensified incision of the mCDW. This retreat propagated from the submarine trough to shallower vicinity and then ceased by the Mid-Holocene coincide with the weakening of the mCDW incision. This phenomenon is consistent with the abrupt ice sheet thinning observed along the eastern coast of the bay (Soya Coast) revealed by surface exposure ages and clear lithofacies change of lake sediments and its AMS C-14 dates. This is the first clear terrestrial and marine-based geological constraint for the large-scale deglaciation of the East AIS, driven by a modulation of the mCDW incision, since the LGM.