[M-IS08] 南大洋・南極氷床が駆動する全球気候変動

[MIS08-P13] Modeling ocean-cryosphere interactions along the Sabrina Coast

*草原 和弥¹、平野 大輔²、藤井 昌和²、Fraser Alexander³、田村 岳史²、溝端 浩平⁴、Williams Guy⁵、青木 茂⁶ (1.海洋研究開発機構、2.国立極地研究所、3.タスマニア大学、4.東京海洋大学、5. 中国海洋大学、6.北海道大学低温研究所)

キーワード：南極と南大洋、氷床/棚氷-海洋相互作用、海洋-海氷-棚氷モデリング

The Totten Ice Shelf (TIS) and Moscow University Ice Shelf (MUIS), along the Sabrina Coast of Wilkes Land, are the floating seaward terminuses of the second largest freshwater reservoir in the East Antarctic Ice Sheets. This glacier/ice-sheet system is a marine-ice-based ice sheet, thus being very vulnerable to the surrounding ocean conditions. Recent comprehensive oceanographic observations, including bathymetric measurements off the Sabrina Coast, shed light on intensive ice-ocean interaction between widespread intrusion of warm modified Circumpolar Deep Water (mCDW) onto the continental shelf and toward the TIS cavity, although spatiotemporal coverage of the observations is very limited. Here, we use an ocean–sea ice–ice shelf model with the recently updated bathymetry to better understand the overall ocean circulations from the shelf break to the TIS cavity and the regional ice-ocean interaction. The model reasonably captured the widespread mCDW intrusion, local sea-ice production, ocean heat and volume transports into the TIS cavity, overturning ocean circulations in the cavities, and the subsequent ice-shelf basal melting. We found notable differences in the temporal variability in ice-shelf basal melting at the two adjacent ice shelves of the TIS and the western part of MUIS (wMUIS). Ocean heat transport by mCDW controls low-frequency variability in ice-ocean interaction along the Sabrina Coast, but the sea-ice production in the Dalton polynya strongly modifies the signals and explains the regional difference between the two. The formation of a summertime eastward-flowing undercurrent beneath the westward-flowing Antarctic slope current is found to play a role in the seasonal ocean heat delivery to the continental shelf.