[M-IS14] Paleoclimatology and paleoceanography

[MIS14-11] Understanding Large-Scale Retreat Mechanisms of the East Antarctic Ice Sheet through Seamless Sea-Land Geological Drilling

*Yusuke Suganuma^1,2, Takuya Itaki³, Yuki Haneda⁴, Kazuya Kusahara⁵, Takashi Obase⁵, Takashige Ishiwa^1,2, Takayuki Omori⁶, Minoru Ikehara⁷, Rob McKay¹⁰, Osamu Seki⁴, Daisuke Hirano^1,2, Masakazu Fujii^1,2, Yuji Kato⁷, Atsuko Amano³, Yuki Tokuda⁹, Hokuto Iwatani⁸, Yoshiaki Suzuki³, Motohiro Hirabayashi¹, Hiroyuki Matsuzaki⁶, Takeyasu Yamagata⁶, Masao Iwai⁷, Kota Katsuki¹¹, Francisco J. Jimenez-Espejo¹², Hiroki Matsui¹³, Koji Seike³, Moto Kawamata¹⁴, Naohisa Nishida¹⁵, Masato Ito¹, Shin Sugiyama⁴, Jun'ichi Okuno^1,2, Takanobu Sawagaki¹⁶, Ayako Abe-Ouchi⁶, Shigeru Aoki⁴, Hideki Miura¹⁷ (1.National institute of Polar Research, 2.The Graduate University for Advanced Studies (SOKENDAI), 3.Geological Survey of Japan, AIST, 4.Institute of Low Temperature Science, Hokkaido University, 5.JAMSTEC, 6.The University of Tokyo, 7.Marine Core Research Institute, Kochi University, 8.Yamaguchi University, 9.Tottori University of Environmental Studies, 10.Antarctic Research Centre, Victoria University of Wellington, 11.Shimane University, 12.Consejo Superior de Investigaciones Científicas-Universidad de Granada, 13.Akita University, 14.Civil Engineering Research Institute for Cold Region, 15.Tokyo Gakugei University, 16.Hosei University, 17.Aomori Public University)

Keywords:Antarctica Ice Sheet, Marine sediments, Be isotope, Circumpolar Deep Water

Recent observations and model simulations indicate that the inflow of warm Circumpolar Deep Water (CDW) drives rapid and significant melting and thinning of the ice shelves in the West Antarctic Ice Sheet (WAIS), contributing to the ongoing increase in grounded ice discharge. This process is also believed to have played a role in the deglaciation of the WAIS after the Last Glacial Maximum (LGM). However, the role of CDW in potential large-scale ice mass loss in the East Antarctic Ice Sheet (EAIS) remains largely unknown. In this study, we present new, well-dated sedimentary core records documenting ice sheet and ice shelf retreat since the LGM, including evidence of ice shelf collapse in Lützow-Holm Bay (LHB), eastern Dronning Maud Land, East Antarctica. Foraminiferal C-14 dating indicates that ice shelf collapse occurred around 9,000 years ago, consistent with the initiation of EAIS thinning revealed by Be-10 surface exposure dating along the southern coast of the bay. Additionally, foraminiferal carbon isotope data from the cores suggest that CDW inflow intensified and reached the southern coast during this period. Using a hierarchical modeling approach that integrates climate and high-resolution ocean simulations, we find that freshwater discharge from adjacent sectors of the EAIS into the Southern Ocean likely enhanced regional CDW inflow into submarine troughs in LHB between 10,000 and 9,000 years ago. Our results suggest that a series of cascading tipping points propagated along the Antarctic margin during the last glacial termination, underscoring the importance of feedback between meltwater input, CDW intrusion onto the continental shelf, ice shelf stability, ice sheet dynamics, and relative sea level rise for both past and future changes in the AIS.