[M-IS08] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS08-05] Holocene deglaciation induced by Circumpolar Deep Water in Lutzow-Holm Bay, East Antarctica

*Yusuke Suganuma^1,2, Moto Kawamata³, Kazuya Kusahara⁵, Nathaniel A Lifton⁶, Takeshige Ishiwa^1,2, Kota Katsuki⁴, Masakazu Fujii^1,2, Motohiro Hirabayashi¹, Jun'ichi Okuno^1,2 (1.National institute of Polar Research, 2.The Graduate University for Advanced Studies (SOKENDAI), 3.Civil Engineering Research Institute for Cold Region, 4.Shimane University, 5.JAMSTEC, 6.Department of Earth, Atmospheric, and Planetary Sciences, Purdue University)

Keywords:Antarctica Ice Sheet and Southern Ocean, large-scale ice mass loss, Surface exposure dating

Recent observations and model simulations show that the inflow of warm Circumpolar Deep Water (CDW) causes rapid melting and thinning of the ice shelves of the West Antarctic Ice Sheet, contributing to the ongoing increase in discharge of grounded ice and to sea-level rise. This process is also thought to contribute to the deglaciation of the West Antarctic Ice Sheet after the Last Glacial Maximum (LGM) ca. 21 ka. However, unlike West Antarctica, the role of the CDW in a potential large-scale ice-mass loss in the East Antarctic is unclear. Here, we present a new, well-constrained ice retreat history since the LGM for Lützow-Holm Bay, East Antarctica, based on a detailed geomorphological survey and ¹⁰Be and ¹⁴C surface exposure dating of erratics and bedrock. These show that ice sheet melting in Lutzow-Holm Bay began in the southeastern part of the bay along the Shirase submarine valley from ca. 9 to 5 ka and eventually spread to the northeast ca. 8–4 ka. Regional high-resolution oceanographic modeling shows that the current warmer ocean temperature in the southeastern part of the bay results from the inflow of warm CDW via the submarine valley. Thus, these oceanographic and bathymetric characteristics likely caused the asymmetric early to mid-Holocene deglaciation in Lützow-Holm Bay, East Antarctica.