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首页> 外文期刊>Journal of Physical Oceanography >A Decomposition of the Atlantic Meridional Overturning Circulation into Physical Components Using Its Sensitivity to Vertical Diffusivity
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A Decomposition of the Atlantic Meridional Overturning Circulation into Physical Components Using Its Sensitivity to Vertical Diffusivity

机译：利用对垂直扩散的敏感性将大西洋子午线翻转环流分解为物理分量

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摘要

The sensitivity of the Atlantic Ocean meridional overturning circulation to the vertical diffusion coefficient κ in the global coupled atmosphere-ocean-sea ice model CLIMBER-3α is investigated. An important feature of the three-dimensional ocean model is its low-diffusive tracer advection scheme. The strength M_(max) of the Atlantic overturning is decomposed into three components: 1) the flow M_S exported southward at 30°S, 2) the large-scale upward flow that balances vertical diffusion in the Atlantic, and 3) a wind-dependent upwelling flux W_(bound) along the Atlantic boundaries that is not due to vertical diffusion. The export of water at 30°S varies only weakly with κ, but is strongly correlated with the strength of the overflow over the Greenland-Scotland ridge. The location of deep convection is found to be mixing dependent such that a shift from the Nordic seas to the Irminger Sea is detected for high values of κ. The ratio R = M_S/M_(max) gives a measure of the interhemispheric overturning efficiency and is found to decrease linearly with κ. The diffusion-induced upwelling in the Atlantic is mostly due to the uniform background value of κ while parameterization of enhanced mixing over rough topography and in stratified areas gives only a weak contribution to the overturning strength. It increases linearly with κ. This is consistent with the classic 2/3 scaling law only when taking the linear variation of the density difference to κ into account. The value of W_(bound) is roughly constant with κ but depends linearly on the wind stress strength in the North Atlantic. The pycnocline depth is not sensitive to changes in κ in the model used herein, and the results suggest that it is primarily set by the forcing of the Southern Ocean winds. The scaling of the total overturning strength with κ depends on the combined sensitivity of each of the terms to κ. In the range of background diffusivity values in which no switch in deep convection sites is detected, M_(max) scales linearly with the vertical diffusivity. It is argued that scalings have, in general, to be interpreted with care because of the generally very small range of κ but also because of possible shifts in important physical processes such as deep convection location.
机译：研究了全球大气海冰联合模型CLIMBER-3α中大西洋经向翻转环流对垂直扩散系数κ的敏感性。三维海洋模型的一个重要特征是其低扩散示踪剂平流方案。大西洋倾覆的强度M_（max）分解为三个部分：1）在30°S向南输出的水流M_S，2）平衡大西洋垂直扩散的大规模向上流动，以及3）非垂直扩散引起的沿大西洋边界的相关上升流W_（bound）。 30°S时的水出口随κ的变化很小，但与格陵兰-苏格兰山脊上溢流的强度密切相关。发现深对流的位置取决于混合，因此对于高κ值，可以检测到从北欧海向艾明格海的转变。比值R = M_S / M_（max）给出了半球翻转效率的度量，并且发现其随κ线性降低。大西洋中扩散引起的上升流主要是由于κ的背景值均匀，而粗糙地形和分层区域中增强混合的参数化仅对倾覆强度做出了微弱的贡献。它随κ线性增加。仅当将密度差的线性变化考虑到κ时，这才符合经典的2/3缩放定律。 W_（bound）的值大致等于κ，但线性取决于北大西洋的风应力强度。在本文使用的模型中，比诺克星深度对κ的变化不敏感，结果表明它主要是由南洋大风的强迫所决定的。总倾覆强度随κ的换算取决于每个项对κ的组合敏感性。在未检测到深对流站点切换的背景扩散率值范围内，M_（max）与垂直扩散率成线性比例关系。有人认为，通常应谨慎解释水垢，因为κ的范围通常很小，而且还因为重要的物理过程（例如深对流位置）可能发生偏移。

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