Parametrizing ocean eddy transfer over continental slopes

参数化大陆坡上的海洋涡流传递

• 批准号: 1538702
• 负责人: Andrew Stewart
• 金额: $ 47.24万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1538702&HistoricalAwards=false
• 关键词: Parametrizing; ocean; eddy; transfer; over

Continental slopes support some of the most influential currents in the world ocean circulation, such as the strong poleward western boundary currents like the Gulf Stream found in the subtropics. However, the circulation across continental slopes is arguably of comparable importance, as they separate shallow coastal waters from the water masses of the deep ocean. Water mass exchanges across continental slopes facilitate upwelling of nutrients to support coastal marine ecosystems, transport heat towards marine-terminating glaciers around Greenland and Antarctica, and control the outflow of dense water masses such as Mediterranean Water and Antarctic Bottom Water. Recent studies point to the importance of mesoscale eddies in modulating both the structure and transport of coastal currents and the cross-slope transfer of water masses and properties. Predictive ocean and climate models are currently unable to resolve these eddies, and are unlikely to routinely resolve the mesoscale globally for at least a couple of decades. Yet despite major recent advances in parametrization strategies for eddies over a flat ocean bed, there have been no concerted attempts to develop analogous strategies for continental slopes. This project aims to close the current gap in understanding mesoscale turbulence over steep slopes, and thereby to develop a parametrization of eddy mixing and transport over continental slopes. This project will provide a graduate student researcher with three years of training in numerical and analytical modeling as well as working knowledge of observational datasets. It also supports an early-career faculty member. A key objective of this project is to produce a set of recommendations for the treatment of mesoscale eddy transport over continental slopes, which will be disseminated widely among the oceanographic and climate communities. Adoption of these practices could substantially improve the representation of shelf and slope processes in large-scale ocean and climate models. The project's model output will be made available to the wider oceanographic community for the purpose of testing and validation. The principal investigator will also participate in outreach activities via existing frameworks supported by his institution.A central goal of this project is to explore the fundamental properties of equilibrated turbulence over continental slopes across a range of forcing conditions, ocean stratifications and slope geometries. The work will characterize the slope?s impact on the eddy life cycle and generation mechanisms, cross- and along-slope eddy transfer of mass and tracers, the routes to dissipation of surface-input momentum and energy, sources and generation of eddy kinetic energy in slope currents, and constraints on the inverse energy cascade and jet formation. In strongly baroclinic coastal currents there is an abundance of potential energy available for the generation of mesoscale eddies, but the availability of energy may be offset by the steep topography, which tends to suppress energy conversion to mesoscale eddy motions. The relative roles of these compensating effects in setting rates of eddy transfer and mixing remains poorly understood. The principal investigator and a graduate student researcher will develop an eddy-resolving process model and create a suite of continental shelf and slope test cases, the output of which will be made available to the wider oceanographic community. This suite of simulations will be used to characterize key properties of slope turbulence, such as the budgets of energy and momentum, and the eddy life cycle. Guided by these findings, the research team will explore several promising theoretical approaches toward the construction of a parametrization of eddy transfer over steep topography. The parametrization will be tested and validated against the suite of eddy-resolving simulations, and against existing databases of satellite-derived sea-surface height data and coastal float release data. The findings of this work will be used to create a set of recommendations and best practices for parametrizing mesoscale eddies over continental slopes, which will be disseminated widely to ocean and climate modelers.

大陆坡支持着世界海洋环流中一些最具影响力的洋流，例如亚热带地区的墨西哥湾流等强烈的向极地西边界洋流。然而，跨大陆坡的环流可以说具有相当的重要性，因为它们将浅海沿岸水域与深海水团分开。跨大陆坡的水团交换促进营养物质的上涌，以支持沿海海洋生态系统，将热量输送到格陵兰岛和南极洲周围的海洋终止冰川，并控制地中海水和南极底水等稠密水团的流出。 最近的研究指出中尺度涡流在调节沿海流的结构和运输以及水团和性质的跨坡转移方面的重要性。预测海洋和气候模型目前无法解决这些涡流，并且至少在几十年内不太可能常规地解决全球中尺度问题。然而，尽管最近在平坦海床上的涡流参数化策略方面取得了重大进展，但尚未一致尝试为大陆坡制定类似的策略。 该项目旨在缩小目前在理解陡坡上中尺度湍流方面的差距，从而开发大陆坡上涡流混合和传输的参数化。该项目将为研究生研究人员提供三年的数值和分析建模培训以及观测数据集的工作知识。它还为职业生涯早期的教员提供支持。该项目的一个关键目标是提出一套处理大陆坡上中尺度涡流传输的建议，这些建议将在海洋学和气候界广泛传播。采用这些做法可以大大改善大规模海洋和气候模型中陆架和斜坡过程的代表性。该项目的模型输出将提供给更广泛的海洋学界进行测试和验证。首席研究员还将通过其机构支持的现有框架参与外展活动。该项目的中心目标是探索在一系列强迫条件、海洋分层和斜坡几何形状下大陆坡上平衡湍流的基本特性。这项工作将描述斜坡对涡流生命周期和产生机制的影响、质量和示踪剂的横向和沿斜坡涡流传递、表面输入动量和能量的耗散路径、斜坡流中涡流动能的来源和产生，以及对逆能量级联和射流形成的约束。在强斜压沿岸流中，有丰富的势能可用于产生中尺度涡流，但可用的能量可能会被陡峭的地形所抵消，而陡峭的地形往往会抑制能量转化为中尺度涡流运动。这些补偿效应在设定涡流传递和混合速率中的相对作用仍然知之甚少。首席研究员和研究生研究员将开发一个涡流解析过程模型，并创建一套大陆架和斜坡测试案例，其输出将提供给更广泛的海洋学界。这套模拟将用于表征斜坡湍流的关键特性，例如能量和动量的预算以及涡流生命周期。在这些发现的指导下，研究小组将探索几种有前途的理论方法，以构建陡峭地形上涡流传递的参数化。参数化将根据涡流解析模拟套件以及现有的卫星海面高度数据和沿海漂浮物释放数据数据库进行测试和验证。这项工作的结果将用于创建一套对大陆坡上的中尺度涡流进行参数化的建议和最佳实践，这些建议和最佳实践将广泛传播给海洋和气候建模者。

项目成果

Scalings for eddy buoyancy transfer across continental slopes under retrograde winds

逆行风下大陆坡涡流浮力传递的尺度

• DOI: 10.1016/j.ocemod.2020.101579
• 发表时间: 2020
• 期刊: Ocean Modelling
• 影响因子: 3.2
• 作者: Wang, Yan;Stewart, Andrew L.
• 通讯作者: Stewart, Andrew L.

Acceleration and Overturning of the Antarctic Slope Current by Winds, Eddies, and Tides

• DOI: 10.1175/jpo-d-18-0221.1
• 发表时间: 2019-07
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: A. Stewart;A. Klocker;D. Menemenlis

Approximating Isoneutral Ocean Transport via the Temporal Residual Mean

通过时间残差平均值近似等中性海洋运输

• DOI: 10.3390/fluids4040179
• 发表时间: 2019
• 期刊: Fluids
• 影响因子: 1.9
• 作者: Stewart, Andrew L.