Southern Ocean ventilation: connection to dynamic tracers and uptake of heat and carbon

由于南极绕极洋流，南大洋在全球具有重要意义，它连接着三个主要的海洋盆地(印度洋、太平洋、大西洋)，并导致全球热量、碳和营养物质的交换。南半球的强西风导致深水的上升流，从而产生了亚南极模式水和南极中间水等模式和中间水域。这些模式的海水向北扩散，使亚热带地区通风，因此可能对全球热量和碳的运输量产生影响。模式水是在冬季结束时形成的，当时南大洋浅滩的非常深的混合层留下了混合良好、均匀的水层。这些模式水被定义在不同大洋盆地的某些密度面上，因为它们的位势涡度很低。利用ECCOv4全球海洋环流模式对南大洋的通风进行了研究，完成了一系列的伴随敏感性实验和正演扰动实验。这些实验将被用来揭示不同的表面强迫如何影响南大洋几种模式水域的形成。这些实验的结果将是识别强迫项，如热通量和风应力，对模式水形成产生影响的敏感度图。然后，我们计划使用正向扰动实验来测试这些线性推论。我们还希望对通风如何影响热量和碳的吸收提供物理上的见解。这种洞察力可能有助于确定随着气候变化导致海洋变暖，南大洋的哪些物理机制可能会发生变化。

The Southern Ocean is globally important due to the Antarctic Circumpolar Current, connecting the three main ocean basins (Indian, Pacific, Atlantic) and leading to the global exchange of heat, carbon, and nutrients. The strong westerly winds in the Southern hemisphere lead to an upwelling of deep waters and thus the creation of mode and intermediate waters, such as Subantarctic Mode Water and Antarctic Intermediate Water. These mode waters spread northward and ventilate the subtropics, and hence can have an impact on the amount of heat and carbon transported around the globe. Mode waters are formed at the end of winter when the very deep mixed layers in the Southern Ocean shoal and leave behind a well-mixed, homogeneous layer of water. These mode waters are defined on certain density surfaces in different ocean basins by their low potential vorticity. The ventilation in the Southern Ocean will be investigated using the ECCOv4 global ocean circulation model to complete a set of adjoint sensitivity experiments and forward perturbation experiments. These experiments will be used to reveal how different surface forcing affects the formation of several mode waters in the Southern Ocean. The outcome from these experiments will be sensitivity maps that identify where forcing terms, such as heat flux and wind stress, have an impact on the formation of mode waters. We then plan to test these linear inferences using forward perturbation experiments. We also hope to provide physical insight into how ventilation affects the uptake of heat and carbon. This insight may be important to help identify which physical mechanisms may change in the Southern Ocean as the ocean warms through climate change.