Dispersion and Mixing Caused By Near-Inertial Internal Waves in Lake Michigan

近惯性内波是海洋和大型湖泊中普遍存在的特征。在沿海海洋中，近惯性内波通常以水平传播的垂直模式存在，但它们的存在和重要性通常被更有活力的内潮所掩盖。然而，在大型湖泊，分层的沿海环境中占主导地位的模态近惯性波，因为没有充满活力的潮汐。因此，这些功能在大型湖泊的研究是有动机的，因为湖泊设置提供了一个独特的实验室，在其中可以研究惯性内波，而不受其他高能过程的干扰。此外，在大型湖泊，惯性内波是一阶的重要性，沿海混合和分散，因为其他机制是缺席和分层是strongly.Intellectual Merit. This项目是基于这样的假设，近惯性内波发挥了重要作用，在密歇根湖和其他五大湖在严重分层，弱强迫夏季期间的垂直混合和水平分散。许多五大湖的环流和扩散研究过滤出惯性周期或更小的时间尺度上的过程，它进一步假设，这种过滤可以有重要的后果，对热，生物群和污染物的垂直混合和水平扩散的推论。本研究的目的有两个。首先，该项目将量化垂直混合在沿海密歇根湖在分层期间，以确定基线湍流混合的幅度和跨温跃层混合的幅度所造成的情节近惯性波;新开发的海洋混合参数化这些波将进行测试。第二，该项目将直接测量水平分散与染料释放的研究和数值模拟的静态和惯性波为主的条件下，明确解决的作用，近惯性波在所谓的增强水平分散。在第一组实验中，其目标是垂直混合，预定的微观结构测量将补充固定系泊的速度和温度，以确定湍流耗散的垂直和跨大陆架的变化及其与可分辨的内波参数的关系。在惯性波事件期间进行的微结构测量将试图量化惯性波周期内湍流的变化。在第二类实验中，目标是水平扩散，将在惯性波事件期间在分层沃茨中进行染料释放实验。染料分散将由普渡大学的自主水下航行器（AUV）进行量化，该航行器将由船只支持。额外的分散工作将使用一个有效的，高分辨率的数值模型密歇根湖和分析的基础上理想化的表示近惯性波在沿海environment.Broader影响：这个项目的更广泛的影响集中在与国家公园管理局的印第安纳州沙丘国家湖岸的合作。普渡大学的自主水下航行器是一种天然的、经过验证的外展工具，将用于与国家公园管理局组织的一系列海滩外展活动，包括演示和教育工作者研讨会。教育工作者研讨会将侧重于培训K-12教育工作者如何纳入五大湖湖沼学的元素，以激励未来的科学家。此外，研究者通过普渡大学夏季本科研究奖学金（SURF）计划指导本科研究人员的既定记录，该项目将支持几名本科研究人员。最后，该项目将成为研究生博士学位的基础。论文，并支持早期职业教师。

Near-inertial internal waves are ubiquitous features in the ocean and large lakes. In the coastal ocean, near-inertial internal waves often exist as horizontally-propagating vertical modes, but their presence and importance is usually overshadowed by more energetic internal tides. However, in large lakes, the stratified coastal environment is dominated by modal near-inertial waves because energetic tides are absent. The study of these features in large lakes is therefore motivated because the lake setting provides a unique laboratory in which one can study inertial internal waves without interference from other energetic processes. Additionally, in large lakes, inertial internal waves are of first order importance for coastal mixing and dispersion because other mechanisms are absent and stratification is strong.Intellectual Merit: This project is based on the hypothesis that near-inertial internal waves play a significant role in vertical mixing and horizontal dispersion in Lake Michigan and other Great Lakes during the heavily stratified, weakly-forced summer period. Many Great Lakes circulation and dispersion studies filter out processes on timescales of inertial period or smaller, and it is further hypothesized that this filtering can have important consequences for inferences drawn about vertical mixing and horizontal dispersion of heat, biota, and pollutants. The objectives of this study are twofold. First, the project will quantify vertical mixing in coastal Lake Michigan during the stratified period, in order to determine the magnitudes of baseline turbulent mixing and the magnitudes of cross-thermocline mixing caused by episodic near-inertial waves; newly-developed oceanic mixing parameterizations for these waves will be tested. Secondly, the project will directly measure horizontal dispersion with dye release studies and numerical modeling for both quiescent and inertial-wave dominated conditions to explicitly resolve the role of near-inertial waves in supposedly heightened horizontal dispersion.Two types of experiments will be conducted. In the first set of experiments, which target vertical mixing, scheduled microstructure measurements will complement fixed moorings of velocity and temperature to determine the vertical and cross-shelf variability of turbulent dissipation and its relationship to resolvable internal wave parameters. Episodic microstructure measurements during inertial wave events will attempt to quantify the variability of this turbulence over the inertial wave cycle. In the second type of experiment, which targets horizontal dispersion, dye release experiments will be performed in stratified waters during inertial wave events. The dye dispersion will be quantified by Purdue's autonomous underwater vehicle (AUV), which will be vessel-supported. Additional dispersion work will be performed using a validated, high-resolution numerical model of Lake Michigan and analysis based on idealized representations of near-inertial waves in the coastal environment.Broader Impacts: The broader impacts of this project are centered on collaboration with the National Parks Service's Indiana Dunes National Lakeshore. Purdue's autonomous underwater vehicle is a natural, proven outreach tool that will be utilized in a set of beach-based outreach activities organized with the National Parks Service, including demonstrations and an educator workshop. The educator workshop will focus on training K-12 educators on how to incorporate elements of Great Lakes limnology to inspire future scientists. Additionally, the investigator has an established record of mentoring undergraduate researchers through the Purdue Summer Undergraduate Research Fellowship (SURF) program, and this project will support several undergraduate researchers. Finally, the project will form the basis of a graduate student's Ph.D. dissertation, and support an early-career faculty member.