Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides
Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides
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DOI：
10.1175/jpo-d-18-0221.1
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发表时间：
2019-07
影响因子：
3.5
通讯作者：
A. Stewart;A. Klocker;D. Menemenlis
中科院分区：
文献类型：
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作者：
A. Stewart;A. Klocker;D. Menemenlis
开阔洋与南极大陆架之间的所有交换都必须经过南极斜坡流（ASC）。以往的研究表明，这些交换强烈的中尺度和潮汐变化的影响，但负责设置ASC的运输和结构的机制得到了相对较少的关注。在这项研究中，风，涡，潮汐加速ASC的作用进行了研究，使用全球海洋海冰模拟非常高的分辨率（1/48°网格间距）。结果表明，地面应力（最终来源于东风）和中尺度涡度通量加速了沿着大陆坡的环流。在大陆架断裂处，ASC显示出一个狭窄（~30-50 km）、快速（>0.2 m s−1）的喷流，与现场观测一致。在这种急流中，表面应力大大减小，甚至可能消失或指向东方，因为海洋表面速度与海冰速度相匹配或超过海冰速度。陆架断裂射流被示出为加速的潮汐动量平流，与潮汐整流的现象相一致。因此，向岸边的Ekman运输消失，因此平均翻转环流，陡峭的南极斜坡锋（ASF）主要是由于潮汐加速。这些研究结果意味着，环流和平均翻转的ASC不仅是由近南极风，但也依赖于海冰覆盖，区域依赖的中尺度涡动活动的大陆坡，和整个大陆架断裂的潮汐流的幅度至关重要。
All exchanges between the open ocean and the Antarctic continental shelf must cross the Antarctic Slope Current (ASC). Previous studies indicate that these exchanges are strongly influenced by mesoscale and tidal variability, yet the mechanisms responsible for setting the ASC’s transport and structure have received relatively little attention. In this study the roles of winds, eddies, and tides in accelerating the ASC are investigated using a global ocean–sea ice simulation with very high resolution (1/48° grid spacing). It is found that the circulation along the continental slope is accelerated both by surface stresses, ultimately sourced from the easterly winds, and by mesoscale eddy vorticity fluxes. At the continental shelf break, the ASC exhibits a narrow (~30–50 km), swift (>0.2 m s−1) jet, consistent with in situ observations. In this jet the surface stress is substantially reduced, and may even vanish or be directed eastward, because the ocean surface speed matches or exceeds that of the sea ice. The shelfbreak jet is shown to be accelerated by tidal momentum advection, consistent with the phenomenon of tidal rectification. Consequently, the shoreward Ekman transport vanishes and thus the mean overturning circulation that steepens the Antarctic Slope Front (ASF) is primarily due to tidal acceleration. These findings imply that the circulation and mean overturning of the ASC are not only determined by near-Antarctic winds, but also depend crucially on sea ice cover, regionally-dependent mesoscale eddy activity over the continental slope, and the amplitude of tidal flows across the continental shelf break.