Ocean Small Eddies Interaction with Large-scale Circulation and Sea Ice

目前所有气候模式都无法解决的1-10公里尺度的海洋“小涡运动”可能显著调节全球海洋环流和海冰。小涡流可以产生很大的垂直速度（10-100米/天），因此可以有效地垂直输送热量/浮力。近地表小涡热通量基本上是向上的，在全球范围内，包括冰雪覆盖地区，在数天至数周的间隔内，其峰值为~1000 W/m2。因此，它可能导致突然和大规模的海冰融化事件。小涡流和它们的浮力通量也被发现活跃地存在于广阔海域的内部和深海。因此，根据变换欧拉平均（TEM）理论，这种小涡浮力通量可能对海洋翻转环流有重要贡献。此外，小涡流可以通过水平和垂直波数之间的能量级联与更大规模的环流交换大量的能量。所有这些影响都可能是显著的，但尚未得到充分或系统的研究。我的研究计划的长期目标是了解海洋环流的基本物理学：它的动力学和能量学，非线性尺度相互作用的影响，以及海洋-冰-大气相互作用。我的短期目标是研究小涡旋（1-10公里）如何在小时到月的时间尺度上与大尺度环流（100公里到全球）和海冰相互作用的基本物理学，通常在过程水平上，使用分析工具和全球到亚盆地尺度的海洋/冰数值模拟层次。我和我的研究小组将把这个项目组织成四个主要目标。第一个目标是根据瞬变电磁学理论研究内部和深海小涡驱动的浮力通量对大尺度翻转环流的贡献，以及如何通过与中尺度涡旋和深海混合的竞争来修正经典的大尺度翻转环流理论。第二个目标是研究小涡流如何通过水平波数和斜压模式的逆级联或正级联非线性地为大尺度环流提供或吸收能量，以及这种能量与海洋深度和位置相互作用的敏感性。第三个目标是研究在模拟和观测中已经部分确定的近地表向上的大强度小涡热通量如何可能导致重大融冰事件并影响北极和南极海冰收支。第四个目标是进行理论研究，了解北大西洋和南大洋混合层下活跃存在的小涡流的产生机制。这项工作将阐明SWOT观测到的小涡过程，SWOT是未来的美法卫星高度计，加拿大也为其做出了贡献。

Ocean "small eddy motions" at scales of 1-10 km, which are unresolved in all current climate models, may significantly modulate the global ocean circulation and sea ice. Small eddies can produce large vertical velocities (10-100 m/day) and hence efficiently transport heat/buoyancy vertically. Near-surface small-eddy heat flux has been found to be essentially upward and peaks at a large magnitude of ~1000 W/m2 over intervals of days to weeks over the globe, including the ice-covered area. Thus it may cause abrupt and large sea-ice melting events. Small eddies and their buoyancy flux are also found to be actively present at the interior and the abyssal of broad ocean areas. Therefore, such small-eddy buoyancy flux may contribute significantly to ocean overturning circulation according to the transformed Eulerian-mean (TEM) theory. Furthermore, small eddies may exchange large amounts of energy with larger-scale circulation via energy cascade across horizontal and vertical wavenumbers. All of these effects will likely be significant, but have not been well or systematically studied. The long-term goal of my research program is to understand the fundamental physics of the ocean circulation: its dynamics and energetics, the impact from nonlinear scale interactions, and the ocean-ice-atmosphere interaction. My short-term goal is to study the fundamental physics of how small eddies (1-10 km) interact with larger-scale circulation (100 km to global) and sea ice over the timescale of hours to months, often at a process level, using analytical tools and a hierarchy of ocean/ice numerical simulations of global to sub-basin scales. My research group and I will organize this program into four main objectives. The first objective is to investigate how small-eddy driven buoyancy fluxes at the interior and abyssal ocean contribute to the large-scale overturning circulation according to the TEM theory, and how this may modify the classic theories of large-scale overturning circulation by competing with mesoscale eddies and abyssal mixing. The second objective is to investigate how small eddies may nonlinearly supply or draw energy for larger-scale circulation through an inverse or forward cascade across horizontal wavenumbers and baroclinic modes, as well as the sensitivity of such energy interaction with ocean depths and locations. The third objective is to study how the large magnitude of near-surface upward small-eddy heat flux, as already partially identified over ice-covered oceans in simulations and observations, may cause significant ice-melting events and affect the Arctic and Antarctic sea ice budget. The fourth objective is to undertake a theoretical study to understand the generation mechanism of small eddies actively present below the mixed layer in the North Atlantic Ocean and the Southern Ocean. This work will shed light on small-eddy processes observable by SWOT, the future USA-French satellite altimeter to which Canada also contributes.