Kinetic Energy Transfers between Mesoscale and Submesoscale Motions in the Open Ocean's Upper Layers
Kinetic Energy Transfers between Mesoscale and Submesoscale Motions in the Open Ocean's Upper Layers
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DOI：
10.1175/jpo-d-21-0099.1
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发表时间：
2022-01-01
影响因子：
3.5
通讯作者：
Griffies, Stephen M.
中科院分区：
文献类型：
--
作者：
Garabato, Alberto C. Naveira;Yu, Xiaolong;Griffies, Stephen M.
中尺度涡旋包含了海洋的大部分动能(KE)，但基本问题仍然存在于连接涡旋产生和消散的跨尺度KE传输上。次中尺度气流的作用代表了讨论的关键点，对次中尺度流动作为中尺度动能的源或汇的看法截然不同。在这里，首次对中尺度和亚中尺度运动之间的动能转移的年度周期进行了观测评估，这是在一个典型的开阔洋区的上层进行的。尽管这些诊断具有边际统计意义，应该谨慎对待，但它们在物理上是可信的，可以为模型评估提供有价值的基准。跨尺度的动能输送有两个不同的阶段，冬季亚中尺度为中尺度输送能量，春季为中尺度输送能量。尽管出现了这种季节性逆转，但在中尺度范围的大部分地区，全年都有一个反向的Ke级联活动。我们的结果与最近的模拟研究并不矛盾，这些研究将逆KE级联的源头放在亚中尺度上，并将中尺度KE的季节性合理地归结为冬季亚中尺度产生的逆级联中介响应。然而，我们的发现可能会挑战这些研究，因为我们认为，在春季，规模较小的KE转移可能会抑制反向KE级联。对中-亚中尺度KE交换动力学的探索性评价表明，冬季高尺度KE输送是由混合层斜压不稳定所支撑的，而春季低尺度KE输送与锋生有关。目前的亚中尺度海洋模式可能大大低估了这种低尺度的动能转移，这是因为这些模式对锋生过程的描述很弱。
Mesoscale eddies contain the bulk of the ocean's kinetic energy (KE), but fundamental questions remain on the cross-scale KE transfers linking eddy generation and dissipation. The role of submesoscale flows represents the key point of discussion, with contrasting views of submesoscales as either a source or a sink of mesoscale KE. Here, the first observational assessment of the annual cycle of the KE transfer between mesoscale and submesoscale motions is performed in the upper layers of a typical open-ocean region. Although these diagnostics have marginal statistical significance and should be regarded cautiously, they are physically plausible and can provide a valuable benchmark for model evaluation. The cross-scale KE transfer exhibits two distinct stages, whereby submesoscales energize mesoscales in winter and drain mesoscales in spring. Despite this seasonal reversal, an inverse KE cascade operates throughout the year across much of the mesoscale range. Our results are not incompatible with recent modeling investigations that place the headwaters of the inverse KE cascade at the submesoscale, and that rationalize the seasonality of mesoscale KE as an inverse cascade-mediated response to the generation of submesoscales in winter. However, our findings may challenge those investigations by suggesting that, in spring, a downscale KE transfer could dampen the inverse KE cascade. An exploratory appraisal of the dynamics governing mesoscale-submesoscale KE exchanges suggests that the upscale KE transfer in winter is underpinned by mixed layer baroclinic instabilities, and that the downscale KE transfer in spring is associated with frontogenesis. Current submesoscale-permitting ocean models may substantially understate this downscale KE transfer, due to the models' muted representation of frontogenesis.