Collaborative Research: Internal Swash zones and boundary-interior exchange: High-accuracy modeling and field observations

合作研究：内部斜流区和边界内部​​交换：高精度建模和现场观察

• 批准号: 1948251
• 负责人: Peter Diamessis
• 金额: $ 93.42万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1948251&HistoricalAwards=false
• 关键词: Collaborative; Research; Internal; Swash; zones

This project will examine how strongly non-linear internal waves (i.e., waves developed at the interface of two fluids with different density) induce mixing near the bed and at the interface of the two fluids. In-situ observations will be carried out in a north-south oriented finger-lake (Lake Cayuga, NY), a natural laboratory with conditions analogous to those found at the edge of the outer continental shelf near the slope during summertime (i.e., warm surface layer overlying a colder layer of water). The analysis of the experimental data combined with sophisticated numerical experiments will provide information that will fill the gap between laboratory work and the most up-to-date oceanographic studies. This work may improve parameterization of boundary fluxes in the ocean, which are important to lateral dispersion of buoyancy, heat, and potentially of organic carbon offshore of productive shelf systems. The work may advance interdisciplinary activities as it may improve communication between physical oceanography and physical limnology. In addition, results may also be pertinent to water quality issues in lakes and coastal areas. Lake Cayuga has been plagued by late-summer algal blooms, while supplying drinking water for the city of Ithaca NY, and for Cornell University. Although this problem is not the direct subject of the study, the data collected will be useful for addressing this societally important issue. The project will support the training of two graduate and one undergraduate student and provide research material that will be integrated in the classroom activities of the principal investigators. The project combines modeling and observations to investigate how nonlinear internal waves (NLIWs) affect near-boundary mixing and boundary-interior exchange events. The objectives are to: 1) explore, in the parameter space of incident internal wave nonlinearity, the mechanisms of NLIW instability, and assess the roles of bottom shear stress, convective/shear instability in the wave front, or bottom boundary layer separation in the wave footprint; 2) quantify and contrast the contribution of each instability type to diapycnal flux generation and boundary-interior exchange (intrusion generation) as a function of incident NLIW energy; 3) determine the role of temporal variability of the advective swash zone and the resulting cyclically incident NLIWs and potential wave-wave interactions, in establishing episodic turbulence, mixing, horizontal transport, and re-stratification of near-bed water. The numerical model is based on high-accuracy spectral element methods, to enable the high- resolution study of internal wave breaking over variable bathymetry. The southern slope and shelf of Lake Cayuga, New York, provides an exceptional natural laboratory for the project field studies, serving as a simpler analog system for the ocean. This lake mimics conditions seen on many summer continental shelves and slopes with a warm surface layer intersecting the shelf, overlying a stratified layer extending down over a steeper bathymetric slope. A low-frequency seiche advects the pycnocline back and forth across the shelf/slope, and hosts higher frequency NLIWs which break near boundaries, mixing the stratified fluid and contributing to expulsion of boundary layer fluid into a basin’s stratified interior. Better understanding of the basic physics will be relevant to a wide range of fields and contribute to better parameterization of the relevant processes.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.

该项目将研究非线性内波(即在不同密度的两种流体的界面上形成的波)如何在床层附近和两种流体的界面上引起混合。现场观测将在一个南北走向的指状湖(纽约州卡尤加湖)进行，这是一个自然实验室，其条件类似于夏季在靠近斜坡的外大陆架边缘发现的条件(即温暖的表层覆盖较冷的水层)。对实验数据的分析与复杂的数值实验相结合，将提供填补实验室工作与最新海洋学研究之间空白的信息。这项工作可能会改进海洋边界通量的参数化，这对生产力陆架系统的浮力、热量和潜在的有机碳在近海的横向扩散很重要。这项工作可以促进跨学科活动，因为它可以改善物理海洋学和物理湖沼学之间的交流。此外，结果还可能与湖泊和沿海地区的水质问题有关。卡尤加湖一直受到夏末藻类水华的困扰，同时也为纽约州伊萨卡市和康奈尔大学提供饮用水。虽然这一问题不是研究的直接主题，但收集的数据将有助于解决这一重要的社会问题。该项目将支持对两名研究生和一名本科生的培训，并提供研究材料，这些材料将纳入首席调查员的课堂活动。该项目将模拟和观测相结合，研究非线性内波(NLIW)如何影响近边界混合和边界-内部交换事件。其目的是：1)在入射内波非线性的参数空间中，探索NLIW不稳定的机制，并评估底部剪切力、波锋中的对流/剪切不稳定或波足迹中的底部边界层分离的作用；2)量化和比较每种不稳定类型对作为入射NLIW能量函数的昼夜通量生成和边界-内部交换(入侵生成)的贡献；3)确定平流区的时间变异性以及由此产生的周期性入射NLIW和潜在的波-波相互作用，在建立幕式湍流、混合、水平输送和近床水的再分层中的作用。数值模型基于高精度谱元方法，以实现变水深内波破裂的高分辨率研究。纽约卡尤加湖的南坡和陆架为该项目的实地研究提供了一个特殊的自然实验室，作为一个更简单的海洋模拟系统。这个湖模仿了许多夏季大陆架和斜坡上的情况，温暖的表层与大陆架相交，覆盖着向下延伸的分层层，向下延伸到更陡峭的水深斜坡上。低频地震使跃层在陆架/斜坡上来回推进，并容纳了频率较高的NLIW，这些NLIW在边界附近破裂，混合了层状流体，有助于将边界层流体排出到盆地的层状内部。更好地理解基础物理学将与广泛的领域相关，并有助于更好地将相关过程参数化。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。