[A-CG46] 北極域の科学

[ACG46-03] Century-long T-S-based estimate of sea ice melt in the Pacific Arctic Region

*Vigan Mensah¹、Yen-Chen Chen²、Kay I. Ohshima^1,3 (1.Institute of Low Temperature Science, Hokkaido University、2.Graduate Institute of Hydrological and Oceanic Science, National Central University, Taiwan、3.Arctic Research Center, Hokkaido University)

キーワード：Sea ice, Pacific Arctic, Atmopshere-Ice-Ocean interactions

The Pacific Arctic Region (PAR: Bering Sea, Chukchi Sea, Beaufort Sea) is an essential region of the Arctic Ocean, as it is connected to both the Atlantic and the Pacific oceans, is a reservoir of fresh water for the ocean, and is strongly influenced by the sea ice cycle. The Bering Sea plays a crucial role in PAR physical and biogeochemical properties. It provides up to 40% of the freshwater flux to the Arctic Ocean, contributes to the stratification of the Pacific Arctic, and is also a primary source of nutrients to this ocean. The Bering Sea only has a seasonal sea ice cover between December and June, and, contrary to the Chukchi and Beaufort seas, no clear trend in sea ice extent, concentration, or production has been detected in it since the beginning of sea ice satellite measurements (1979). In this study, we use historical data of ocean temperature and salinity from 1930 to 2020 to estimate sea ice melt and establish meltwater thickness climatologies spanning the periods before and after 1980 (i.e., the beginning of satellite measurements), with the main focus on the Bering Sea. The estimated ice melt amounts are consistent both qualitatively and quantitatively with ice thickness data obtained from the CRYOSAT-2-SMOS merged product. Our results reveal a decrease in sea ice melt of 15% between the two climatological periods. To further confirm this trend, we also produced decadal climatologies of the Bering Sea winter water salinity, which is used as a proxy for sea ice production. These climatologies also revealed a significant salinity decrease (-0.14) between 1940-1960 and 2000-2020. Lastly, vertical profiles of climatological salinity indicate an increase in sea surface salinity and a decrease in sub-surface salinity after 1980. All three variables that we estimated are thus consistent in indicating a decrease in sea ice production and sea ice melt in the Bering Sea, whose start occurred before the beginning of the satellite era. Besides this analysis, preliminary results of ice melt in the Chukchi and Beaufort seas will also be presented.