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

密歇根湖近惯性内波引起的色散和混合

• 批准号: 1030842
• 负责人: Cary Troy
• 金额: $ 40.66万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1030842&HistoricalAwards=false
• 关键词: Dispersion; Mixing; Caused; Near; Inertial

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.

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高能量的内潮所掩盖。然而，在大型湖泊中，分层的海岸环境以模式近惯性波为主，因为没有高能潮汐。因此，在大型湖泊中研究这些特征是有动机的，因为湖泊环境提供了一个独特的实验室，人们可以在其中研究惯性内波，而不会受到其他能量过程的干扰。此外，在大型湖泊中，惯性内波对海岸混合和扩散具有一阶重要性，因为缺乏其他机制，层结作用很强。智力上的优点：该项目基于这样的假设，即在层化程度较高、强迫较弱的夏季期间，近惯性内波对密歇根湖和其他五大湖的垂直混合和水平扩散起着重要作用。许多五大湖环流和扩散研究过滤掉了惯性周期或更小时间尺度上的过程，并进一步假设这种过滤可以对关于热量、生物群和污染物的垂直混合和水平扩散的推断产生重要的影响。这项研究的目的有两个。首先，该项目将量化分层期间密歇根湖沿岸的垂直混合，以确定基准线湍流混合的量级和由幕式近惯性波引起的跨温跃层混合的量级；将检验为这些波新开发的海洋混合参数。其次，该项目将通过静态和惯性波为主的条件下的染料释放研究和数值模拟来直接测量水平色散，以明确地解决近惯性波在假定的水平色散增强中的作用。将进行两种类型的实验。在第一组实验中，以垂直混合为目标，预定的微结构测量将补充固定的速度和温度停泊，以确定湍流耗散的垂直和跨陆架可变性及其与可分辨内波参数的关系。惯性波事件期间的幕式微结构测量将试图量化这种湍流在惯性波周期中的变化。在以水平扩散为目标的第二类实验中，染料释放实验将在惯性波事件期间在分层水中进行。染料的分散性将由普渡大学的自主水下机器人(AUV)量化，该机器人将由船只支持。其他扩散工作将使用密歇根湖经过验证的高分辨率数值模型，并基于沿海环境中近惯性波的理想化表示进行分析。更广泛的影响：该项目的更广泛影响集中在与国家公园服务的印第安纳沙丘国家湖岸的合作上。普渡大学的自主水下机器人是一种自然的、经过验证的推广工具，将用于与国家公园管理局共同组织的一系列海滩推广活动，包括演示和教育工作者研讨会。教育家研讨会将重点培训K-12教育工作者如何融入五大湖湖沼学的元素，以激励未来的科学家。此外，研究人员有通过普渡大学夏季本科生研究奖学金(SURF)项目指导本科生研究人员的既定记录，该项目将支持几名本科生研究人员。最后，该项目将构成研究生博士论文的基础，并支持一名职业生涯早期的教师。

项目成果

Shear dispersion from near-inertial internal Poincaré waves in large lakes: Shear dispersion in stratified large lakes

大型湖泊中近惯性庞加莱内波的剪切色散：分层大型湖泊中的剪切色散

• DOI: 10.1002/lno.10163
• 发表时间: 2015
• 期刊: Limnology and Oceanography
• 影响因子: 4.5
• 作者: Choi, Jun M.;Troy, Cary D.;Hawley, Nathan
• 通讯作者: Hawley, Nathan

Spatial structure of internal Poincaré waves in Lake Michigan

密歇根湖庞加莱内波的空间结构

• DOI: 10.1007/s10652-013-9294-3
• 发表时间: 2014
• 期刊: Environmental Fluid Mechanics
• 影响因子: 2.2
• 作者: Ahmed, Sultan;Troy, Cary D.;Hawley, Nathan
• 通讯作者: Hawley, Nathan

Logarithmic velocity structure in the deep hypolimnetic waters of L ake M ichigan

密歇根湖深浅层水域的对数速度结构

• DOI: 10.1002/2014jc010506
• 发表时间: 2016
• 期刊: Journal of Geophysical Research: Oceans
• 作者: Troy, Cary;Cannon, David;Liao, Qian;Bootsma, Harvey
• 通讯作者: Bootsma, Harvey