On eddy transport in the ocean. Part II: The advection tensor
On eddy transport in the ocean. Part II: The advection tensor
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DOI：
10.1016/j.ocemod.2021.101845
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发表时间：
2021-09
期刊：
影响因子：
3.2
通讯作者：
M. Haigh;Luolin Sun;J. McWilliams;P. Berloff
中科院分区：
文献类型：
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作者：
M. Haigh;Luolin Sun;J. McWilliams;P. Berloff
本研究考虑涡旋分辨双涡旋准地转海洋环流中质量和被动示踪物的等密涡旋输送。在这里，我们专注于平流输送，而配套文件的重点是涡流引起的扩散示踪剂输送。为了使涡流示踪剂运输参数化，我们使用空间滤波器定义的涡流的运输张量来量化涡流示踪剂通量，这导致与通过时间雷诺涡流分解获得的结果不同的结果。平流张量是输运张量的反对称部分，之所以这样命名，是因为相关的示踪剂输运可以表示为大尺度示踪剂场的平流，由具有流函数A的旋转涡诱导速度（EIV）u c表示。在涡动活动最强的地方，例如在上层，靠近东向急流和西边界流的地方，EIV u c是最快的（101 ms− 1）。我们的研究结果表明，一个随机封闭的涡流运输将是最合适的，因为A表现出概率分布时，例如，大尺度的相对涡度的条件。与海洋环流模式中的封闭相一致，我们将涡动质量（等密度层厚度）通量量化为涡动引起的平流，其厚度为EIV u h。发散的部分u-100 h的质量输送相关的准地转极限的唯一部分往往是面向下的厚度梯度，这表明它量化了一些斜压涡效应类似的参数化的根特和麦克威廉姆斯（GM 90）EIV。虽然u h有一些定性的相似性u c，我们的研究结果表明，涡诱导示踪剂平流驱动的不仅仅是厚度确定的EIV，反过来，不仅仅是GM 90 EIV。
This study considers the isopycnal eddy transport of mass and passive tracers in eddy-resolving double-gyre quasigeostrophic oceanic circulation. Here we focus on advective transport, whereas a companion paper focuses on eddy-induced diffusive tracer transport. To work towards parameterising eddy tracer transport we quantify the eddy tracer flux using a transport tensor with eddies defined using a spatial filter, which leads to results distinct from those obtained via a temporal Reynolds eddy decomposition. The advection tensor is the antisymmetric part of the transport tensor, and is so named since the associated tracer transport can be expressed as advection of the large-scale tracer field by a rotational eddy-induced velocity (EIV) u∗ c with streamfunction A. The EIV u∗ c is fastest (∼ 1 ms− 1) where eddy activity is strongest, eg, in the upper layer, near the eastward jet and western boundary current. Our results suggest that a stochastic closure for the eddy transport would be most suitable since A exhibits a probabilistic distribution when conditioned on, for example, the large-scale relative vorticity. Consistent with closures in ocean circulation models, we quantify eddy mass (isopycnal layer thickness) fluxes as eddy-induced advection by the thickness EIV u∗ h. The divergent part of u∗ h–the only part relevant for mass transport in the quasigeostrophic limit–tends to be oriented down the thickness gradient suggesting it quantifies some baroclinic eddy effects similar to those parameterised by the Gent & McWilliams (GM90) EIV. Although u∗ h has some qualitative similarities to u∗ c, our results suggest that eddy-induced tracer advection is driven by more than just the thickness-determined EIV and, in turn, more than just the GM90 EIV.