[M-IS14] 古気候・古海洋変動

[MIS14-11] 海-陸シームレス地層掘削から探る東南極氷床の大規模融解メカニズム

*菅沼 悠介^1,2、板木 拓也³、羽田 裕貴⁴、草原 和弥⁵、小長谷 貴志⁵、石輪 健樹^1,2、大森 貴之⁶、池原 実⁷、McKay Rob¹⁰、関 宰⁴、平野 大輔^1,2、藤井 昌和^1,2、加藤 悠爾⁷、天野 敦子³、徳田 悠希⁹、岩谷 北斗⁸、鈴木 克明³、平林 幹啓¹、松崎 浩之⁶、山形 武靖⁶、岩井 雅夫⁷、香月 興太¹¹、Jimenez-Espejo Francisco¹²、松井 浩紀¹³、清家 弘治³、川又 基人¹⁴、西田 尚央¹⁵、伊藤 優人¹、杉山 慎⁴、奥野 淳一^1,2、澤柿 教伸¹⁶、阿部 彩子⁶、青木 茂⁴、三浦 英樹¹⁷ (1.国立極地研究所、2.総合研究大学院大学、3.産業技術総合研究所、4.北海道大学低温科学研究所、5.海洋研究開発機構、6.東京大学、7.高知大学海洋コア研究所、8.山口大学、9.鳥取環境大学、10.Antarctic Research Centre, Victoria University of Wellington、11.島根大学、12.Consejo Superior de Investigaciones Científicas-Universidad de Granada、13.秋田大学、14.寒地土木研究所、15.東京学芸大学、16.法政大学、17.青森公立大学)

キーワード：南極氷床、海底堆積物、ベリリウム同位体、周極深層水

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.