Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic
Testing Munk's hypothesis for submesoscale eddy generation using observations in the North Atlantic
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DOI：
10.1002/2017jc012910
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发表时间：
2017-08
影响因子：
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通讯作者：
Christian E. Buckingham;Zammath Khaleel;A. Lazar;Adrian P. Martin;J. Allen;A. N. Garabato;A. Thompson;C. Vic
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文献类型：
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作者：
Christian E. Buckingham;Zammath Khaleel;A. Lazar;Adrian P. Martin;J. Allen;A. N. Garabato;A. Thompson;C. Vic
为了了解亚中尺度涡旋的形成机制，研究人员结合水文测量，利用高分辨率卫星图像揭示了沿海锋边缘的一系列连贯的亚中尺度（6公里）涡旋。红外卫星图像包含北大西洋中纬度（48.69°N, 16.19°W）的内联图像分辨率为m的海洋表面温度。伴随的高度观测加上有规律的涡旋间距表明，涡旋是由中尺度搅拌、细丝化和随后的锋面不稳定造成的。虽然水平切变或正压不稳定性（BTI）是产生这种涡旋的一种机制（Munk假设），但我们从线性理论结合现场数据得出结论，混合层或亚中尺度斜压不稳定性（BCI）是观测到的亚中尺度涡旋更合理的解释。在这里，我们假设锋面扰动保持在线性增长阶段，并被线性动力学准确地描述。这一结果可能更适用于公海，即沿海地区和强洋流系统内梯度罗斯比数相对其值减少的地区。鉴于这类水域占海洋表面的相当大比例，而且能量和浮力通量在BTI和BCI下不同，这一结果对公海能量/浮力收支和海洋环流模式的参数化具有更广泛的影响。总之，这项工作提供了在开放海洋中由BCI产生亚中尺度涡的罕见观测证据。
A high-resolution satellite image that reveals a train of coherent, submesoscale (6 km) vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies. The infrared satellite image consists of ocean surface temperatures at inline image m resolution over the midlatitude North Atlantic (48.69°N, 16.19°W). Concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring, filamentation, and subsequent frontal instability. While horizontal shear or barotropic instability (BTI) is one mechanism for generating such eddies (Munk's hypothesis), we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability (BCI) is a more plausible explanation for the observed submesoscale vortices. Here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics. This result likely has greater applicability to the open ocean, i.e., regions where the gradient Rossby number is reduced relative to its value along coasts and within strong current systems. Given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under BTI and BCI, this result has wider implications for open-ocean energy/buoyancy budgets and parameterizations within ocean general circulation models. In summary, this work provides rare observational evidence of submesoscale eddy generation by BCI in the open ocean.