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首页> 外文期刊>Journal of Physical Oceanography >Abrupt Transitions in Submesoscale Structure in Southern Drake Passage: Glider Observations and Model Results
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Abrupt Transitions in Submesoscale Structure in Southern Drake Passage: Glider Observations and Model Results

机译：南德雷克通道亚中尺度结构的突然转变：滑翔机观测和模型结果

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摘要

Enhanced vertical velocities associated with submesoscale motions may rapidly modify mixed layer depths and increase exchange between the mixed layer and the ocean interior. These dynamics are of particular importance in the Southern Ocean, where the ventilation of many density classes occurs. Here we present results from an observational field program in southern Drake Passage, a region preconditioned for submesoscale instability owing to its strong mesoscale eddy field, persistent fronts, strong down-front winds, and weak vertical stratification. Two gliders sampled from December 2014 through March 2015 upstream and downstream of the Shackleton Fracture Zone (SFZ). The acquired time series of mixed layer depths and buoyancy gradients enabled calculations of potential vorticity and classifications of submesoscale instabilities. The regions flanking the SFZ displayed remarkably different characteristics despite similar surface forcing. Mixed layer depths were nearly twice as deep, and horizontal buoyancy gradients were larger downstream of the SFZ. Upstream of the SFZ, submesoscale variability was confined to the edges of topographically steered fronts, whereas downstream these motions were more broadly distributed. Comparisons to a one-dimensional (1D) mixing model demonstrate the role of submesoscale instabilities in generating mixed layer variance. Numerical output from a submesoscale-resolving simulation indicates that submesoscale instabilities are crucial for correctly reproducing upper-ocean stratification. These results show that bathymetry can play a key role in generating dynamically distinct submesoscale characteristics over short spatial scales and that submesoscale motions can be locally active during summer months.
机译：与亚中尺度运动相关的增强的垂直速度可能会迅速改变混合层的深度，并增加混合层与海洋内部之间的交换。这些动力学在发生许多密度等级通风的南部海洋特别重要。在这里，我们介绍南部地区德雷克海峡的观测野外观测结果，该地区由于其中等规模的涡流场，持续的锋面，强烈的前锋前风和弱的垂直分层而为亚中尺度的不稳定性做好了准备。 2014年12月至2015年3月，在沙克尔顿断裂带（SFZ）上游和下游采样了两个滑翔机。所获得的混合层深度和浮力梯度的时间序列使得能够进行潜在涡度的计算以及亚中尺度不稳定性的分类。尽管有相似的表面作用力，但SFZ两侧的区域仍显示出明显不同的特性。混合层深度几乎是深度的两倍，而SFZ下游的水平浮力梯度更大。在SFZ上游，亚中尺度的变化仅限于地形导向锋面的边缘，而下游这些运动分布更广。与一维（1D）混合模型的比较表明，亚中尺度不稳定性在生成混合层方差中的作用。亚尺度分解模拟的数字输出表明，亚尺度尺度的不稳定性对于正确再现上层海洋分层至关重要。这些结果表明，测深法可以在短空间尺度上动态生成不同的亚中尺度特征中发挥关键作用，并且亚中尺度的运动在夏季可以局部活跃。

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