Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean
Enhancement of Mesoscale Eddy Stirring at Steering Levels in the Southern Ocean
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DOI：
10.1175/2009jpo4201.1
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发表时间：
2010-01-01
影响因子：
3.5
通讯作者：
Shuckburgh, Emily
中科院分区：
文献类型：
--
作者：
Abernathey, Ryan;Marshall, John;Shuckburgh, Emily
提出并讨论了南大洋有效扩散率的经向截面。的有效扩散系数，K-eff，表征率中尺度涡旋搅拌性能的内部等密度表面和横向在海面上。通过监测的速度，涡流搅拌理想化的示踪剂，其初始分布单调变化的南极绕极流（ACC）的分布。在没有观测到的地图，在内部海洋的涡流，平流速度场是从一个涡流允许状态估计的南大洋（SOSE）。通过在水平表面和等密度表面上应用中村技术求解三维对流扩散方程并诊断扩散率。由此得到的K-eff的纬向剖面显示，在ACC之下的一个层中，等密涡动增强（达到类似于2000 m（2）s（-1）的值），但在赤道侧翼向表面上升。低有效扩散率值（类似于500米（2）秒（-1））被发现在表面附近的平均流量的ACC是最强的。本文认为，K-eff在斜压波的操纵层附近增强，这是沿着ACC轴深，但浅的赤道侧翼。K-eff的值也被发现是空间相关的等密面上的位涡梯度和大的梯度是弱的，反之亦然，从简单的动力参数预期。最后，讨论了K-eff空间分布对ACC动力学及其翻转环流的意义。
Meridional cross sections of effective diffusivity in the Southern Ocean are presented and discussed. The effective diffusivity, K-eff, characterizes the rate at which mesoscale eddies stir properties on interior isopycnal surfaces and laterally at the sea surface. The distributions are obtained by monitoring the rate at which eddies stir an idealized tracer whose initial distribution varies monotonically across the Antarctic Circumpolar Current (ACC). In the absence of observed maps of eddying currents in the interior ocean, the advecting velocity field is taken from an eddy-permitting state estimate of the Southern Ocean (SOSE). A three-dimensional advection-diffusion equation is solved and the diffusivity diagnosed by applying the Nakamura technique on both horizontal and isopycnal surfaces. The resulting meridional sections of K-eff reveal intensified isopycnal eddy stirring (reaching values of similar to 2000 m(2) s(-1)) in a layer deep beneath the ACC but rising toward the surface on the equatorward flank. Lower effective diffusivity values (similar to 500 m(2) s(-1)) are found near the surface where the mean flow of the ACC is strongest. It is argued that K-eff is enhanced in the vicinity of the steering level of baroclinic waves, which is deep along the axis of the ACC but shallows on the equatorial flank. Values of K-eff are also found to be spatially correlated with gradients of potential vorticity on isopycnal surfaces and are large where those gradients are weak and vice versa, as expected from simple dynamical arguments. Finally, implications of the spatial distributions of K-eff for the dynamics of the ACC and its overturning circulation are discussed.