Eddy stirring in the Southern Ocean
Eddy stirring in the Southern Ocean
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DOI：
10.1029/2010jc006818
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发表时间：
2011-09-17
影响因子：
3.6
通讯作者：
Polzin, K. L.
中科院分区：
文献类型：
--
作者：
Garabato, A. C. Naveira;Ferrari, R.;Polzin, K. L.
关于南极绕极流中涡旋搅动的分布及其控制过程的性质一直存在争议。这个问题是解决在这里估计的等熵涡动扩散系数卡帕从收集的水文和测高观测，分析混合长度的理论框架。结果表明，通常情况下，卡帕抑制的数量级在上公里的ACC正面射流相对于他们的周围环境，主要是由于混合长度的局部减少。根据Ferrari和Nikurashin（2010）推导的标度律，通过宽正压急流涡旋搅拌的准地转理论再现了这一观测结果。该理论解释所观察到的广泛抑制的混合长度和卡帕在上层的正面射流作为运动学的结果，涡传播相对于射流核心内的平均流。在一些特殊的地点，会遇到偏离上层海洋急流核心混合抑制的普遍制度的情况。这种“漏射流”的部分似乎与尖锐的固定曲折的平均流量所产生的ACC与主要地形特征的相互作用。有人争辩说，南大洋的特征温盐结构，由多个上层海洋温盐锋分离和均匀的属性区域的基础上，主要是由于广泛抑制涡流搅拌平行射流。
There is an ongoing debate concerning the distribution of eddy stirring across the Antarctic Circumpolar Current (ACC) and the nature of its controlling processes. The problem is addressed here by estimating the isentropic eddy diffusivity kappa from a collection of hydrographic and altimetric observations, analyzed in a mixing length theoretical framework. It is shown that, typically, kappa is suppressed by an order of magnitude in the upper kilometer of the ACC frontal jets relative to their surroundings, primarily as a result of a local reduction of the mixing length. This observation is reproduced by a quasi-geostrophic theory of eddy stirring across a broad barotropic jet based on the scaling law derived by Ferrari and Nikurashin (2010). The theory interprets the observed widespread suppression of the mixing length and kappa in the upper layers of frontal jets as the kinematic consequence of eddy propagation relative to the mean flow within jet cores. Deviations from the prevalent regime of mixing suppression in the core of upper-ocean jets are encountered in a few special sites. Such 'leaky jet' segments appear to be associated with sharp stationary meanders of the mean flow that are generated by the interaction of the ACC with major topographic features. It is contended that the characteristic thermohaline structure of the Southern Ocean, consisting of multiple upper-ocean thermohaline fronts separated and underlaid by regions of homogenized properties, is largely a result of the widespread suppression of eddy stirring by parallel jets.