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首页> 外文期刊>Journal of Physical Oceanography >Equilibration of the Antarctic Circumpolar Current by Standing Meanders
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Equilibration of the Antarctic Circumpolar Current by Standing Meanders

机译：站立弯道平衡南极绕极电流

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The insensitivity of the Antarctic Circumpolar Current (ACC)'s prominent isopycnal slope to changes in wind stress is thought to stem from the action of mesoscale eddies that counterbalance the wind-driven Ekman overturning-a framework verified in zonally symmetric circumpolar flows. Substantial zonal variations in eddy characteristics suggest that local dynamics may modify this balance along the path of the ACC. Analysis of an eddy-resolving ocean GCM shows that the ACC can be broken into broad regions of weak eddy activity, where surface winds steepen isopycnals, and a small number of standing meanders, across which the isopycnals relax. Meanders are coincident with sites of (ⅰ) strong eddy-induced modification of the mean flow and its vertical structure as measured by the divergence of the Eliassen-Palm flux and (ⅱ) enhancement of deep eddy kinetic energy by up to two orders of magnitude over surrounding regions. Within meanders, the vorticity budget shows a balance between the advection of relative vorticity and horizontal divergence, providing a mechanism for the generation of strong vertical velocities and rapid changes in stratification. Temporal fluctuations in these diagnostics are correlated with variability in both the Eliassen-Palm flux and bottom speed, implying a link to dissipative processes at the ocean floor. At larger scales, bottom pressure torque is spatially correlated with the barotropic advection of planetary vorticity, which links to variations in meander structure. From these results, it is proposed that the "flexing" of standing meanders provides an alternative mechanism for reducing the sensitivity of the ACC's baroclinicity to changes in forcing, separate from an ACC-wide change in transient eddy characteristics.
机译：人们认为，南极绕极电流（ACC）的主要等腰斜率对风应力的变化不敏感，这是由于中尺度涡旋的作用抵消了中风涡旋Ekman倾覆的作用-在纬向对称的绕极流中验证了这一框架。涡流特征的明显区域性变化表明，局部动力学可能会改变沿ACC路径的这种平衡。对解析涡旋的海洋GCM的分析表明，ACC可以分为涡旋活动较弱的广阔区域，在该区域表面风使等渗陡峭，而少数站立曲折使等渗缓和。曲流与（ⅰ）强涡引起的平均流及其垂直结构的变化点重合，这是通过Eliassen-Palm通量的发散和（ⅱ）深涡动能最多增加两个数量级来测量的在周边地区。在曲折范围内，旋涡性预算显示出相对旋涡性对流与水平散度之间的平衡，为产生强大的垂直速度和分层迅速变化提供了一种机制。这些诊断程序中的时间波动与Eliassen-Palm通量和海底速度的变化有关，这暗示着与海床耗散过程的联系。在更大范围内，底部压力转矩在空间上与行星涡度的正压对流相关，而正涡对流与曲折结构的变化有关。根据这些结果，提出了站立曲折的“弯曲”提供了一种替代机制，用于降低ACC斜压对强迫变化的敏感性，与ACC范围内瞬态涡流特性的变化分开。

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