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 km 尺度的海洋“小涡流运动”在所有当前气候模型中均未解决，但可能会显着调节全球海洋环流和海冰。小涡流可产生较大的垂直速度（10-100 m/天）和因此，已发现近地表小涡流热通量基本上是向上的，并且在数天内达到约 1000 W/m2 的峰值。因此，在全球范围内，包括被冰覆盖的区域，它可能会导致突然的、大规模的海冰融化事件，并且它们的浮力通量也被发现活跃地存在于广阔的海洋区域的内部和深渊。 ，根据变换欧拉平均（TEM）理论，这种小涡流浮力通量可能对海洋翻转环流有显着贡献。此外，小涡流可以通过能量级联与更大规模的环流交换大量能量。所有这些影响可能都很重要，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：其动力学和能量学、影响。我的短期目标是研究小涡流（1-10 公里）如何与大尺度环流（100 公里到全球）和海冰相互作用的基础物理学。在几个小时的时间范围内几个月，通常在过程层面，使用分析工具和全球到次流域尺度的海洋/冰数值模拟的层次结构，我和我的研究小组将这个项目分为四个主要目标。根据 TEM 理论，内海和深海小涡驱动的浮力通量对大规模翻转环流有贡献，以及这如何通过与中尺度涡流和中尺度涡流竞争来修改大规模翻转环流的经典理论。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反向或正向级联非线性地供应或吸取能量以进行更大规模的环流，以及这种能量与海洋深度和位置相互作用的敏感性。第三个目标是研究大量的近地表向上小涡热通量（正如在模拟和观测中已经在冰覆盖的海洋上部分确定的那样）可能会导致重大的冰融化事件并影响第四个目标是进行理论研究，以了解北大西洋和南大洋混合层下方活跃的小涡流的产生机制。这项工作将揭示小涡流过程。可以通过 SWOT 观测到，SWOT 是未来的美国-法国卫星高度计，加拿大也对此做出了贡献。