An study on the change characteristics of summer hydrographic structure in the Cosmonaut Sea
Based on observational data obtained by Chinese Antarctic expeditions(CHINARE37-38),this study analyzed the changed characteristics of the summer hydrographic structure in the Cosmonaut Sea,taking into consideration of the sea ice concentration,World Ocean Atlas 2023 Climate Normal Fields Data,and ERA5 reanalysis data.It was found that the water masses in the Cosmonaut Sea include Antarctic Surface Water(including Summer Surface Water(SSW)and Winter Water(WW)),Circumpolar Deep Water(CDW),Modified CDW,and Antarctic Bottom Water.The SSW had depth of<50 m,and it exhibited a trend of cold in the south and warm in the north.The greatest thickness of WW was south of 66°S,with its maximum depth of approximately 200 m.There was an obvious trend of southward invasion of CDW,and the upwelling height of CDW found in CHINARE-38 was 10-20 m higher than that in CHINARE-37.Because SSW in the ice-free area receives solar shortwave radiation over a long duration,the core of SSW in the central ice-free area of the sea was found to have high temperature and high salinity,while SSW in local coastal areas was cool and fresh owing to ice meltwater.The wind field in the central area of the Cosmonaut Sea maintains a cyclonic circulation,and subsurface water rises and cools the warm surface water through Ekman pumping,which leads to enhanced mixing between surface and subsurface waters,and southward invasion and upwelling of CDW.
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