Generation of the Internal Pycnocline in the Subpolar Southern Ocean by Wintertime Sea Ice Melting
Generation of the Internal Pycnocline in the Subpolar Southern Ocean by Wintertime Sea Ice Melting
复制标题
冬季海冰融化在副极地南大洋产生内部密斜斜
作者：
Klocker A
海洋内部的密度跃层是一层升高的分层，将通风良好的上层海洋与更新较慢的深海分开。尽管它在组织海洋环流中起着关键作用，但内部密度跃层形成的过程仍然知之甚少。关于密度跃层形成的经典理论是以温度为依据的，目前尚不清楚该理论如何适用于高纬度的南大洋，那里的分层主要是由盐度决定的。在这里，我们通过分析高分辨率、现实的全球海冰-海洋模型来评估南部高纬度地区产生内部密度跃层的机制。我们发现的证据表明，内部密度跃层的形成与两个不同的冰覆盖区域的海冰-海洋相互作用有关，这两个区域位于南极大陆斜坡和冬季海冰边缘。在这两个地区，冬季持续的海冰融化在冬季混合层的底部产生了强烈的基于盐度的分层。由此产生的高分层片随后下降到海洋内部的南极绕极流的前端，并无缝连接到内部密度跃层在更北的地区，其中密度跃层层是由温度决定的。因此，我们的研究结果表明，局部海冰-海洋相互作用在配置南大洋的垂直结构中发挥着重要作用。
The ocean's internal pycnocline is a layer of elevated stratification that separates the well‐ventilated upper ocean from the more slowly renewed deep ocean. Despite its pivotal role in organizing ocean circulation, the processes governing the formation of the internal pycnocline remain little understood. Classical theories on pycnocline formation have been couched in terms of temperature and it is not clear how the theory applies in the high‐latitude Southern Ocean, where stratification is dominated by salinity. Here we assess the mechanisms generating the internal pycnocline at southern high latitudes through the analysis of a high‐resolution, realistic, global sea ice–ocean model. We show evidence suggesting that the internal pycnocline's formation is associated with sea ice‐ocean interactions in two distinct ice‐covered regions, fringing the Antarctic continental slope and the winter sea‐ice edge. In both areas, winter‐persistent sea‐ice melt creates strong, salinity‐based stratification at the base of the winter mixed layer. The resulting sheets of high stratification subsequently descend into the ocean interior at fronts of the Antarctic Circumpolar Current, and connect seamlessly to the internal pycnocline in areas further north in which pycnocline stratification is determined by temperature. Our findings thus suggest an important role of localized sea ice‐ocean interactions in configuring the vertical structure of the Southern Ocean.