南极宇航员海夏季水文结构变化特征研究

An study on the change characteristics of summer hydrographic structure in the Cosmonaut Sea

本文基于中国南极考察(CHINARE37-38)在宇航员海获取的海洋综合站位观测数据,结合海冰密集度、WOA23和ERA5再分析资料等,分析了该海域主要水文结构及其变化特征。结果表明:宇航员海夏季水团包括南极表层水(分为夏季表层水与冬季残留水)、绕极深层水、变性绕极深层水和南极底层水。夏季表层水均分布在表层50 m深度以浅,呈现出南冷北暖的趋势。66°S以南的冬季残留水最厚,最深可达200 m左右。绕极深层水向南侵入的趋势明显,CHINARE-38绕极深层水向上涌升的高度较CHINARE-37高出10~20 m。夏季表层水的高温高盐核心位于中心海域无冰区,因为无冰海域的表层海水长时间接收太阳短波辐射而温度较高。近岸海域因冰融水导致局部夏季表层水降温淡化。宇航员海中心海域海面风场维持低气压气旋式环流,次表层水体通过Ekman抽吸上升冷却表层暖水,导致表层与次表层水体混合加强,绕极深层水向南侵入并向上涌升。

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.