The Combined Effect of Tidally and Eddy-Driven Diapycnal Mixing on the Large-Scale Ocean Circulation
The Combined Effect of Tidally and Eddy-Driven Diapycnal Mixing on the Large-Scale Ocean Circulation
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DOI：
10.1175/jpo-d-11-0122.1
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发表时间：
2012-04-01
影响因子：
3.5
通讯作者：
Lee, Warren G.
中科院分区：
文献类型：
--
作者：
Saenko, Oleg A.;Zhai, Xiaoming;Lee, Warren G.
最近的一些研究表明，海洋西部边界是涡动能量耗散的主要区域。在全球范围内，涡流能量汇已被估计为集成约0.2 TW。这是一个相当大的一部分潮汐能耗散在深海内部，估计约为1.0 TW，并有助于diapycnal混合。作者进行敏感性实验与海洋环流模式假设涡动能量被分散到高波数垂直模式，导致能量耗散和局部增强diapycnal混合。当只有潮能耗散维持底辟混合时，翻转环流和深海层结都很弱。随着涡动耗散的增加，深海热结构更接近于观测结果，海底的翻转环流和层结更强。此外，与涡流耗散相关联的混合可以单独驱动相对较强的翻转。深海层结和翻转对底辟混合的垂直结构十分敏感。当这些能量大部分在海底以上300米范围内消散时，深海的翻转和分层作用就太弱了。允许耗散渗透到更高的水柱中，如最近的观测所建议的，导致更强的分层和纬向环流。纬向环流也受到影响。特别是，德雷克通道运输变得更接近其观测估计与地形上方的湍流的垂直尺度的增加。与一些理论模型相一致，德雷克通道输送量随着平均上层海洋扩散率的增加而增加。
Several recent studies have shown that ocean western boundaries are the primary regions of eddy energy dissipation. Globally, the eddy energy sinks have been estimated to integrate to about 0.2 TW. This is a sizable fraction of the tidal energy dissipation in the deep oceanic interior, estimated at about 1.0 TW and contributing to diapycnal mixing. The authors conduct sensitivity experiments with an ocean general circulation model assuming that the eddy energy is scattered into high-wavenumber vertical modes, resulting in energy dissipation and locally enhanced diapycnal mixing. When only the tidal energy dissipation maintains diapycnal mixing, the overturning circulation, and stratification in the deep ocean are too weak. With the addition of the eddy dissipation, the deep-ocean thermal structure becomes closer to that observed and the overturning circulation and stratification in the abyss become stronger. Furthermore, the mixing associated with the eddy dissipation can, on its own, drive a relatively strong overturning. The stratification and overturning in the deep ocean are sensitive to the vertical structure of diapycnal mixing. When most of this energy dissipates within 300 m above the bottom, the abyssal overturning and stratification are too weak. Allowing for the dissipation to penetrate higher in the water column, such as suggested by recent observations, results in stronger stratification and meridional circulation. Zonal circulation is also affected. In particular, the Drake Passage transport becomes closer to its observational estimates with the increase in the vertical scale for turbulence above topography. Consistent with some theoretical models, the Drake Passage transport increases with the increase in the mean upper-ocean diffusivity.