Collaborative Research: Internal Lee-Wave Dissipation in Oceanic Flows with Mean Shear

合作研究：平均剪切海洋流中的内部利波耗散

• 批准号: 1755313
• 负责人: Amit Tandon
• 金额: $ 17.37万
• 依托单位: University of Massachusetts, Dartmouth
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-15 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1755313&HistoricalAwards=false
• 关键词: Collaborative; Research; Internal; Lee; Wave

The mechanisms for dissipating the ocean's balanced flow remain uncertain but are important for correctly simulating oceanic circulation. Dissipation through internal lee-wave generation followed by turbulence production has been proposed to account for 20-75% of the needed loss. However, microstructure measurements do not agree with the predicted dissipation. This research will explain this discrepancy and better constrain the role of lee-waves in dissipating vs. redistributing energy. This study will carry out numerical simulations describing the generation, propagation, dissipation, and reabsorption of internal lee-waves in areas where earth rotation-induced flows of finite extent are dominant. Results from this project will be presented at conferences and published in peer-reviewed journals to make them available to the wider scientific community. The results of this study will provide an improved parameterization for the dissipation and redistribution of balanced flows and induced mixing by lee-wave generation and increase the accuracy of Ocean circulation modeling. The project will support education and mentoring of a graduate student in numerical modeling and internal-wave physics, and an undergraduate student in research. The research will also be utilized in outreach activities for the general public and K-12 science teachers, as well as undergraduate and international student training.Large amounts of power, equivalent of 1 TW, is thought to be input into the ocean circulation by wind-work. The maintenance of steady state conditions (i.e., constant energy levels) in the world's oceans requires that addition of energy by the wind is balanced through energy dissipation processes. Internal lee-wave generation has been assumed to be one of the largest predicted energy sinks dissipating 0.2 to 0.75 TW through turbulence generation. However, measurements in Antarctic Circumpolar Current jets find that turbulent dissipation rates fall short of predictions by as much as an order of magnitude. Recent numerical simulations of spontaneous near-inertial wave generation in the Kuroshio Front find that much of the generated wave energy is reabsorbed back into the mean flow. If reabsorption also occurs for lee waves, they would be as much a mechanism for redistributing balanced energy as dissipating it. These numerical simulations will determine what fractions of lee-wave energy are lost to turbulence vs. being reabsorbed into the mean flow and hence address whether lee-wave generation represents a major sink for the large-scale circulation. Missing key elements have been sheared flow and wave action (E/w) conservation where E is the wave energy density, w = kU the Lagrangian frequency of the lee wave, k the topographic wavenumber and U the flow speed. In a bottom-intensified rotating shear flow, the fraction kU1/(kUo) is available for dissipation and (kUo- kU1)/(kUo) for reabsorption, where Uo is the bottom flow speed and U1 f/k the flow where the waves break. The numerical simulations will test realistic ocean flow and topography configurations to determine whether reabsorption is a significant fraction of lee-wave generation in the ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

消散海洋平衡流量的机制仍然不确定，但对于正确模拟海洋循环非常重要。通过内部李波生成的耗散，随后提出了湍流产生，以占所需损失的20-75％。但是，微观结构测量与预测的耗散不一致。这项研究将解释这种差异，并更好地限制Lee波在消散能量与重新分布能量中的作用。这项研究将进行数值模拟，描述内部Lee波的产生，繁殖，耗散和重吸收，在大地旋转引起的有限程度的流动占主导地位的地区。该项目的结果将在会议上介绍，并在同行评审的期刊上发表，以使其可以向更广泛的科学界提供。这项研究的结果将为平衡流量的耗散和重新分布提供改进的参数化，并通过Lee-Wave产生引起混合，并提高海洋循环建模的准确性。该项目将支持数值建模和内波物理学研究生的教育和指导，以及研究生研究生。这项研究还将用于公众和K-12科学教师以及本科和国际学生培训的外展活动。据认为，相当于1 TW的实力量被认为是通过风能投入到海洋循环中的。在世界海洋中维持稳态条件（即恒定能级），要求通过耗能耗散过程平衡风能。内部李波的产生被认为是最大的预测能量水槽之一，通过湍流产生耗散0.2至0.75 TW。但是，南极圆极电流喷气机的测量发现，湍流耗散速率的预测量不得超过一个数量级。在黑素前阵线中自发的近惯性波产生的最新数值模拟发现，许多生成的波能都被重新吸收到平均流中。如果李波还会发生重吸收，它们将是重新分布平衡能量的机制，与消散它一样。这些数值模拟将确定李波能量的部分因湍流而损失了，而被重新吸收到平均流量中，因此解决了Lee-Wave的产生是否代表了大规模循环的主要水槽。缺失的密钥元素是剪切的流动和波动作用（E/W）保护，其中E是波能密度，w = ku，Lee波的拉格朗日频率，k地形波数和u流速。在底部强化的旋转剪切流中，ku1/（kuO）的分数可用于耗散，并且（kuo-ku1）/（kuo）可重吸收，其中uo是底部流速和u1 f/k，波浪的流量是波浪破裂的流量。数值模拟将测试现实的海洋流量和地形配置，以确定重吸收是否是海洋中Lee-Wave产生的很大一部分。该奖项反映了NSF的法定任务，并被认为值得通过基金会的知识分子优点和更广泛的影响审查标准通过评估来进行评估。

项目成果

Topographically Generated Submesoscale Shear Instabilities Associated with Brazil Current Meanders

与巴西海流曲流相关的地形产生的亚尺度剪切不稳定性

• DOI: 10.1175/jpo-d-22-0122.1
• 发表时间: 2023
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Luko, Caique D.;Lazaneo, Cauê Z.;Silveira, Ilson C.;Pereira, Filipe;Tandon, Amit
• 通讯作者: Tandon, Amit