[M-IS16] Paleoclimatology and paleoceanography

[MIS16-11] Reconstruction of the ice sheet history since the Last Glacial Maximum based on field-based geomorphological observations and surface exposure ages along the southern Soya Coast, Lützow-Holm Bay, East Antarctica

*Moto Kawamata¹, Yusuke Suganuma^2,1, Koichiro Doi^2,1, Keiji Misawa^2,1, Motohiro Hirabayashi², Akihisa Hattori¹, Takanobu Sawagaki³ (1.Department of Polar Science, School of Multidisciplinary Science, SOKENDAI (The Graduate Unversity for Advanced Studies), 2.National Institute of Polar Research, 3.Hosei University)

Keywords:East Antarctic Ice Sheet, Glacial geomorphology, Surface exposure dating, Marine ice-sheet instability, Ice sheet history

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.