南极樊尚湾大陆架mCDW入侵影响下的水体结构演变特征分析

Evolution of water structure under the influence of mCDW intrusion on the continental shelf of Vincennes Bay,Antarctica

利用象海豹CTD观测到的2012年3—10月南极樊尚湾海域的温盐剖面数据,研究结冰期该海域陆架区变性绕极深层水(mCDW)入侵影响下的水体结构演变过程。结果显示,从湾口到湾最内侧的深层都存在显著的mCDW入侵。结冰过程中来自海表的冷却和析盐作用从上方向海洋内部延伸,而到6月中旬湾最内侧的400 dbar以深层结依然没被打破。湾最内部的西侧冰架前缘C区域和沿岸冰间湖D区域具有不同的水体结构特征。结冰初期,C区域的300~600 dbar深度范围内持续存在冰架水(ISW),其上下都出现θ>–1.7℃的高温核,说明mCDW携带的热量可能致使该深度范围内冰架融化。D区域海水热含量明显高于C区域,可知mCDW携带更多热量进入D区域。另外,结冰后期(9—10月)冰间湖区域水体特性垂向趋于一致,直接反映深对流的存在,致使高密度陆架水的产生和积累。

Using seal CTD data obtained in Vincennes Bay(Antarctica) during March–October 2012, this study investigated the evolution of water structure on the continental shelf under the influence of the intrusion of modified Circumpolar Deep Water(mCDW) during the freezing period. Results showed obvious mCDW intrusion in the deep layer from the bay mouth to the innermost part of the bay. Effects from cooling and brine rejection during sea ice formation extended from the upper layer into the interior;however, deep layer(>400 dbar) stratification in the innermost part of the bay remained unbroken until mid-June. Under the different influences of heat brought by mCDW, the glacier front C-Zone and the polynya D-Zone of the innermost bay exhibited different water structure characteristics. From early April to June, Ice Shelf Water(ISW) persisted at depths of 300–600 dbar in the C-Zone with warm cores(θ >-1.7℃) above and below, indicating that the heat carried by mCDW causes melting of the ice shelf within this depth range, while the meltwater of the ice shelf cools the seawater. Ocean heat content in the D-Zone was substantially higher than that in the C-Zone,and ISW was found below 400 dbar only in early April. Therefore, mCDW carries more heat into the D-Zone,and melting of the ice shelf in the D-Zone might occur over a deeper range. Additionally, during the late freezing period(September – October), the vertical characteristics of the water in polynyas tend to be homogeneous,proving the existence of deep convection for the formation and accumulation of Dense Shelf Water.