Oceanic motions with spatial scales of 200 m–20 km, called submesoscales, are ubiquitous in the upper ocean and serve as a key intermediary between larger-scale balanced dynamics and unbalanced turbulence. Here, we introduce the fluid dynamics of submesoscales and contrast them with motions at larger and smaller scales. We summarize the various ways in which submesoscales develop due to instabilities that extract potential or kinetic energy from larger-scale balanced currents; some instabilities have counterparts at larger scales, while others are distinct to the submesoscale regime. Submesoscales modify the density stratification in the upper ocean and redistribute energy between scales. These energy transfers are complex, having both up-scale and down-scale components. Submesoscale eddies and fronts also contribute to a spatially heterogeneous distribution of shear and restratification that leave an imprint on upper ocean turbulence. The impact of submesoscales on the Earth's climate remains an exciting research frontier.

中文翻译：

---

上层海洋的亚尺度动力学


空间尺度为 200 m-20 km 的海洋运动（称为亚中尺度）在上层海洋中普遍存在，是大尺度平衡动力学与不平衡湍流之间的关键中介。在这里，我们介绍了亚介尺度的流体动力学，并将其与更大和更小尺度的运动进行对比。我们总结了由于不稳定性从更大规模的平衡电流中提取势能或动能而导致亚介尺度发展的各种方式；一些不稳定现象在更大尺度上有对应的现象，而另一些则与亚中尺度体系不同。次中尺度改变了上层海洋的密度分层并在尺度之间重新分配能量。这些能量转移很复杂，既有高尺度的成分，也有低尺度的成分。次中尺度涡流和锋面也导致了剪切和再分层的空间异质分布，从而在上层海洋湍流中留下了印记。亚中尺度对地球气候的影响仍然是一个令人兴奋的研究前沿。