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: 1948578
• 负责人: Erika McPhee-Shaw
• 金额: $ 39.67万
• 依托单位: Western Washington 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=1948578&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.

该项目将检查如何强烈的非线性内部波（即，在两个具有不同密度的流体的界面上发育的波）如何诱导床附近和两种流体的界面诱导混合。原位观察结果将在一个面向南北的手指湖（纽约州卡尤加湖）中进行，这是一种天然实验室，其条件类似于夏季期间斜坡附近外大陆架边缘（即温暖的表面上的温度层，层上冷层的温暖的表面层）类似。对实验数据与复杂数值实验相结合的分析将提供信息，以填补实验室工作与最新海洋学研究之间的空白。这项工作可以改善海洋边界通量的参数化，这对于浮力，热量以及生产货架系统的有机碳离岸的横向分散很重要。这项工作可能会推进跨学科活动，因为它可以改善物理海洋学和物理林记之间的沟通。此外，结果也可能与湖泊和沿海地区的水质问题有关。卡尤加湖（Lake Cayuga）在为纽约市伊萨卡市（Ithaca Ny）和康奈尔大学（Cornell University）提供饮用水时，遭到了晚夏季藻类的困扰。尽管此问题不是研究的直接主题，但收集的数据对于解决这一至关重要的问题很有用。该项目将支持两名研究生和一名本科生的培训，并提供将集成在主要研究人员的课堂活动中的研究材料。该项目结合了建模和观察结果，以研究非线性内部波（NLIWS）如何影响近边界混合和边界间交换事件。目的是：1）在事件内波非线性的参数空间中探索NLIW不稳定性的机制，并评估底部剪切应力，对流/剪切不稳定性在波浪前或底部边界层在波脚印中的作用； 2）量化和对比每种不稳定性类型对Diapynal通量产生和边界间交换（入侵产生）的贡献是入射NLIW能量的函数； 3）确定活动偏压区域的临时变异性以及所得的周期性入射NLIW和潜在波波相互作用的作用，在建立情节性湍流，混合，水平运输和重新分层近床中的作用。数值模型基于高临界光谱元素方法，以实现对可变测深的内波破裂的高分辨率研究。纽约Cayuga湖的南坡和架子为项目现场研究提供了出色的天然实验室，它是海洋的简单模拟系统。这个湖泊模仿条件在许多夏季大陆架子和槽中都看到了温暖的表面层与架子相交，并覆盖了一个分层的层，延伸到钢铁测深坡上。低频Seiche冒险将在整个架子/斜坡上来回pycnocline，并容纳较高的频率NLIWS，这些频率在边界接近边界，将分层的流体混合在一起，并有助于将边界层流体驱逐到盆地分层的内部。更好地了解基本物理学将与各种领域有关，并有助于更好地参数化相关过程的参数化。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子和更广泛的影响评估审查标准，认为通过评估被认为是珍贵的支持。