[M-IS03] The Southern Ocean and the Antarctic Ice Sheet dynamics in past, present and future

[MIS03-02] Warm surface waters increase Antarctic ice shelf melt and delay dense water formation

*青木 茂¹、髙橋 智樹¹、山崎 開平¹、平野 大輔²、小野 数也¹、草原 和弥³、田村 岳史²、ウィリアムス ガイ⁴ (1.北海道大学、2.国立極地研究所、3.海洋研究開発機構、4.タスマニア大学)

キーワード：南大洋、棚氷、南極表層水

Melting ice shelves around Antarctica control the massive input of freshwater into the ocean and play an intricate role in global heat redistribution. The Amery Ice Shelf (AIS) regulates wintertime sea-ice growth and dense shelf water formation. We investigated the role of warm Antarctic Surface Water (AASW) in AIS melting and its impact on dense shelf water. Here we show that the coastal ocean in summer 2016/17 was almost sea-ice free, leading to higher AASW temperatures. The glacial meltwater fraction in AASW was the highest in the previous record, hypothesised to be attributable to anomalous AIS melting. The excess heat and freshwater in early 2017 delayed the seasonal evolution of dense shelf water. Focused on ice shelf melting at depth, the importance and impacts of warming surface waters has been overlooked. In a warming climate, increased surface water heating will reduce sea-ice and potentially Antarctic Bottom Water formation.