Modifications of gyre circulation by sub-mesoscale physics
Modifications of gyre circulation by sub-mesoscale physics
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DOI：
10.1016/j.ocemod.2010.04.001
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发表时间：
2010-01-01
期刊：
影响因子：
3.2
通讯作者：
Takahashi, K.
中科院分区：
文献类型：
--
作者：
Levy, M.;Klein, P.;Takahashi, K.
通过在水平分辨率（1 度、1/9 度和 1/54 度）变化的一系列数值实验中比较盆地尺度、季节性变化、副热带和副极地环流的平均特征来解决亚介尺度物理的大尺度影响，相应地，在亚网格尺度混合中。经过 100 年的模拟，正如早期研究表明的那样，当分辨率从 1 度切换到 1/9 度时，通风温跃层的平均环流和平均结构存在很大差异。我们的结果强调，将分辨率从 1/9 度增加到 1/54 度会导致进一步的重大变化。这些变化是由于 1/54 度处出现了更密集、更有活力的涡旋群而产生的，该涡旋群占据了盆地的大部分区域，并由亚中尺度物理维持。这种湍流的非线性效应强烈增强了分离两个环流的射流，从而使等密度线变得陡峭，并抵消了强涡流驱动的热传输（使它们趋于扁平化）。喷流更具纬向性，向东渗透得更远，并向南移动了几度，这显着改变了环流的形状和位置。主喷流的加强伴随着与复杂再循环相关的高能次要纬向喷流区域的出现。与此同时，亚中尺度重新分层了季节性和主要温跃层，特别是引起了深层对流的减少和参与经向翻转环流的水团的改变。尽管这里提出的结果可能受到我们盆地理想化几何形状的高度限制，但它们表明亚中尺度过程对大洋盆地尺度的平均环流和平均输送发挥着重要作用。在此处呈现的最高分辨率（1/54 度）下，动量效应变得越来越重要，因此涡流不仅会导致等密度线的塌落，而且可以安排流动以形成在某些地方具有更陡峭的等密度线的喷射状结构。 (C) 2010 Elsevier Ltd. 保留所有权利。
The large-scale impacts of sub-mesoscale physics are addressed by comparing mean characteristics of basin-scale, seasonally varying, subtropical and subpolar gyres in a suite of numerical experiments varying in horizontal resolution (1 degrees, 1/9 degrees and 1/54 degrees) and accordingly, in sub-grid scale mixing. After 100 years of simulation, and as suggested from earlier studies, the mean circulation and the mean structure of the ventilated thermocline strongly differ when switching from 1 degrees to 1/9 degrees resolution. Our results emphasize that increasing the resolution from 1/9 degrees to 1/54 degrees leads to major further changes. These changes ensue from the emergence of a denser and more energetic vortex population at 1/54 degrees, occupying most of the basin and sustained by sub-mesoscale physics. Non-linear effects of this turbulence strongly intensify the jet that separates the two gyres, thus steepening the isopycnals and counter-balancing the strong eddy-driven heat transport that tends to flatten them. The jet is more zonal, penetrates further to the east, and is shifted southward by a few degrees, which significantly alters the shape and position of the gyres. The strengthening of the main jet comes together with the emergence of a regime of energetic secondary zonal jets, associated with complex recirculations. In parallel, sub-mesoscales restratify both the seasonal and the main thermocline, inducing in particular a reduction of deep convection and the modification of the water masses involved in the meridional overturing circulation. Although the results presented here are presumably highly constrained by the idealized geometry of our basin, they suggest that sub-mesoscale processes play an important role on the mean circulation and mean transports at the scale of oceanic basins. At the highest resolution presented here (1/54 degrees), momentum effects are becoming important so that eddies do not simply cause the slumping of isopycnals but can arrange the flow to form jet-like structures with steeper isopycnals in places. (C) 2010 Elsevier Ltd. All rights reserved.