09:00 〜 09:15
[MIS16-11] 東南極リュツォ・ホルム湾に面する宗谷海岸南部地域における野外地形調査と表面露出年代を基にした氷床融解過程の復元
キーワード：東南極氷床、氷河地形、表面露出年代、Marine ice-sheet instability、氷床変動史
The thinning and retreat history of the East Antarctic Ice Sheet (EAIS) since the Last Glacial Maximum (LGM) is essential for understanding the mechanisms and drivers of the large-scale and potentially non-linear (abrupt) response of the ice sheet melting. Such information is needed to assess and capture the key process enacting of abrupt deglaciation over this century and beyond for the future prediction. However, a detailed reconstruction of the history of the EAIS involving changes in its thickness and lateral extent since the LGM remains sparse. Here, we show a new detailed ice sheet history from the southern Soya Coast, Lützow-Holm Bay, East Antarctica, based on field-based geomorphological observations and surface exposure ages. Our results demonstrate that the ice sheet completely covered the highest peak of Skarvsnes (400 m a.s.l.) prior to ~9 ka and retreated eastward by at least 10 km during the Early to Mid-Holocene (ca. 9 to 6 ka). The timing of the abrupt ice-sheet thinning and retreat is consistent with the intrusion of modified Circumpolar Deep Water into deep submarine valleys in Lützow-Holm Bay, as inferred from fossil foraminifera records of marine sediment cores. Thus, we propose that the process of marine ice-sheet instability and ocean-driven melting most likely cause the abrupt thinning and retreat of the EAIS along the southern Soya Coast since the LGM. Such abrupt ice-sheet thinning and retreat with similar magnitude and timing have also been reported from an outlet glacier from Enderby Land, East Antarctica. This geological evidence emphasizes the importance of understanding paleo ice-sheet changes based on geological and geomorphological study not only in West Antarctica but also in East Antarctica to predict potential ice mass loss areas associated with the ocean–ice-sheet interactions in the future.