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Six circumpolar currents - on the forcing of the Antarctic Circumpolar Current by wind and mixing

机译：六个极电流-风和混合作用迫使南极极电流

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The transport of the Antarctic Circumpolar Current (ACC) is influenced by a variety of processes and parameters. A proper implementation of basin geometry, ocean topography and baroclinicity is known to be a fundamental requisite for a realistic simulation of the circulation and transport. Other, more subtle parameters are those of eddy-induced transports and diapycnal mixing of thermohaline tracers or buoyancy, either treated by eddy resolution or by a proper parameterization. Quite a number of realistic numerical simulations of the circulation in the Southern Ocean have recently been published. Many concepts on relations of the ACC transport to model parameters and forcing function are in discussion, however, without much generality and little success. We present a series of numerical simulations of circumpolar flow with a simplified numerical model, ranging from flat-bottom wind-driven flow to baroclinic flow with realistic topography and wind and buoyancy forcing. Analysis of the balances of momentum, vorticity, and baroclinic potential energy enables us to develop a new transport theory, which combines the most important mechanisms driving the circulation of the ACC and determining its zonal transport. The theory is based on the importance of the bottom vertical velocity in generating vorticity and shaping the baroclinic potential energy of the ACC. It explains the breaking of the f/h-constraint by baroclinicity and brings together in one equation the wind and buoyancy forcing of the current. The theory emphasizes the role of Ekman pumping and eddy diffusion of buoyancy to determine the transport. It also demonstrates that eddy viscosity effects are irrelevant in the barotropic vorticity balance and that friction arises via eddy diffusion of density. In this regime, the classical Stommel model of vorticity balance is revived where the bottom friction coefficient is replaced by K/X2 (with the Gent-McWilliams coefficient K and the baroclinic Rossby radius λ) and a modified wind curl forcing appears.
机译：南极绕极电流（ACC）的传输受多种过程和参数的影响。正确实现流域几何形状，海洋地形和斜压度是现实模拟环流和输运的基本条件。其他更微妙的参数是涡旋感应的输运和热盐示踪剂或浮力的水向混合，这些参数可以通过涡旋分辨率或适当的参数化处理。最近已经发表了许多关于南大洋环流的逼真的数值模拟。但是，关于ACC传输与模型参数和强制函数的关系的许多概念都在讨论中，但是没有太多的通用性，也没有什么成功。我们用简化的数值模型提供了一系列绕极流的数值模拟，范围从平底风力驱动流到具有现实地形以及风和浮力强迫的斜压流。对动量，涡度和斜压势能平衡的分析使我们能够开发新的输运理论，该理论结合了驱动ACC循环并确定其区域输运的最重要机制。该理论基于底部垂直速度在产生涡旋和调整ACC斜压势能中的重要性。它解释了斜压力对f / h约束的破坏，并通过一个方程式将电流的风和浮力强加在一起。该理论强调了埃克曼泵送和浮力的涡流扩散对确定运输的作用。它还表明涡流粘度效应与正压涡旋平衡无关，并且摩擦是通过密度的涡流扩散而产生的。在这种情况下，经典的Stommel涡度平衡模型得以恢复，其中底部摩擦系数被K / X2（具有Gent-McWilliams系数K和斜压Rossby半径λ）代替，并且出现了改进的风卷强迫。

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