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

海洋小涡流与大尺度环流和海冰的相互作用

• 批准号: RGPIN-2021-03667
• 负责人: Su, Zhan
• 金额: $ 2.19万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762718
• 关键词: Ocean; Small; Eddies; Interaction; Large

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.

1-10公里尺度的海洋“小涡旋运动”在所有现有气候模式中都没有得到解决，可能对全球海洋环流和海冰产生重大影响。小涡流可以产生大的垂直速度（10-100米/天），因此可以有效地垂直输送热量/浮力。近地表的小涡热通量基本上是向上的，在地球仪上，包括冰层覆盖的地区，每隔几天到几周，其峰值达到约1000 W/m2。因此，它可能会造成突然和大规模的海冰融化事件。在广阔海洋区域的内部和深海也发现活跃的小涡旋及其浮力通量。因此，这种小涡浮力通量可能有助于显着的海洋翻转环流根据转换欧拉平均（TEM）理论。此外，小涡旋还可以通过水平波数和垂直波数的能量级联与大尺度环流进行大量的能量交换。所有这些影响可能都很重要，但尚未得到很好或系统的研究。我的研究计划的长期目标是了解海洋环流的基本物理：我的短期目标是研究小涡旋（1-10公里）如何与大尺度环流相互作用的基础物理（100公里到全球）和海冰在几个小时到几个月的时间尺度，往往在一个过程的水平，使用分析工具和海洋/冰的全球到子流域尺度的数值模拟层次。我的研究小组和我将组织这个计划分为四个主要目标。第一个目标是根据TEM理论研究内部和深海小涡旋驱动的浮力通量如何对大规模翻转环流做出贡献，以及这如何通过与中尺度涡旋竞争来修改大规模翻转环流的经典理论。和深海混合。第二个目标是研究小涡旋如何通过跨越水平波数和斜压模式的反向或正向级联，非线性地为大尺度环流提供或汲取能量，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在冰层覆盖的海洋上的大幅度近地表向上的小涡流热通量如何可能造成重大的冰融化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的小涡旋的生成机制。这项工作将阐明小涡过程可观察的SWOT，未来的美国-法国卫星高度计，加拿大也有助于。