Collaborative research: Coastal inertial-band dynamics: separating forced and free responses in a natural laboratory

合作研究：沿海惯性带动力学：在自然实验室中分离受迫响应和自由响应

• 批准号: 1635166
• 负责人: Jonathan Nash
• 金额: $ 12.09万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635166&HistoricalAwards=false
• 关键词: Collaborative; research; Coastal; inertial; band

Surface winds globally impart about half a terawatt of energy to inertial oscillations in the surface mixed layer. The coastal ocean receives less wind work than the open ocean because it has less surface area. However, near-inertial wave generation is enhanced along coastlines, because the boundary induces large convergences and divergences in mixed-layer velocities. This process is dynamically significant because it transfers energy from forced surface-trapped motions to free motions, which can produce currents and turbulence in the stratified interior. Idealized theories and observations of the coastal ocean have confirmed the generation and propagation of near-inertial waves, but observational studies have not yet separated free and forced motions so that internal-wave generation, energy flux, and dissipation can be accurately quantified. Furthermore, the results of individual studies have not been synthesized to estimate the global significance or geography of coastal near-inertial wave generation. This project will improve the dynamical understanding and prediction of near inertial motions throughout the coastal ocean, in marginal seas, and in large lakes. The fieldwork will also contribute to our knowledge of the geophysical dynamics of Lake Superior, a valuable resource that is under-sampled with respect to physical measurements. These contributions include the first broad-scale turbulence measurements in the lake and the extension of a multi-year time series of density and currents. Coinciding measurements of chlorophyll fluorescence, turbidity, and oxygen will also illuminate the presently unknown relationships between turbulence and biogeochemistry in Lake Superior. The project will also develop tools and lessons for graduate oceanography and limnology courses, and support citizen science in Duluth, MN, via the development of a public drifter-building program in conjunction with the local office of the Environmental Protection Agency. The project will also train a PhD student and two undergraduate summer researchers.This project aims to quantify coastal kinetic-energy pathways from wind work to dissipation, and produce a detailed description of coastal inertial-band dynamics by extending existing theories of coastal near-inertial wave generation and definitively testing them. This will be done using realistic numerical simulations and intensive direct observations of wind work, mixed-layer and stratified turbulence, and near-inertial internal-wave generation, propagation, and dissipation along a coastline and over rough coastal topography. Specifically, extensive observations will collected in Lake Superior, which is dominated by near-inertial motions during summer and has negligible tides, weak mean circulation, and little river input, making it also an ideal laboratory of the coastal ocean. The observations will include broad-scale measurements of turbulence from ship-based surveys and Wirewalker wave-powered moored profilers. Three traditional moorings will also be deployed for four years, extending an existing time series that can be used to identify extreme events and long-term trends in near-inertial motions. The project also includes novel analyses of analytical and numerical models, which will aid in the collection and interpretation of observations and enable the results in Lake Superior to be extended throughout the coastal ocean using historical wind, stratification, and bathymetry data.

全球表面风向表面混合层的惯性振荡传递约半太瓦的能量。沿海海洋比公海接受的风功更少，因为它的表面积较小。然而，沿着海岸线，近惯性波的产生增强，因为边界引起混合层速度的大收敛和发散。这个过程在动力学上具有重要意义，因为它将能量从受迫的表面俘获运动转移到自由运动，这可以在分层内部产生电流和湍流。理想化理论和沿海海洋观测已经证实了近惯性波的产生和传播，但观测研究尚未将自由运动和受迫运动分开，从而能够准确量化内波的产生、能量通量和耗散。此外，尚未综合个别研究的结果来估计沿海近惯性波产生的全球意义或地理。该项目将提高对整个沿海海洋、边缘海和大型湖泊中近惯性运动的动力学理解和预测。实地工作还将有助于我们了解苏必利尔湖的地球物理动力学，这是一种在物理测量方面采样不足的宝贵资源。这些贡献包括首次对湖中的大尺度湍流测量以及密度和水流的多年时间序列的扩展。对叶绿素荧光、浊度和氧气的同时测量也将阐明苏必利尔湖湍流与生物地球化学之间目前未知的关系。该项目还将为研究生海洋学和湖沼学课程开发工具和课程，并通过与环境保护局当地办公室合作开发公共漂流者建设计划，支持明尼苏达州德卢斯的公民科学。该项目还将培训一名博士生和两名本科生暑期研究人员。该项目旨在量化从风功到耗散的沿海动能路径，并通过扩展现有的沿海近惯性理论来详细描述沿海惯性带动力学波的产生并最终测试它们。这将通过对风功、混合层和分层湍流以及沿着海岸线和崎岖的海岸地形的近惯性内波的产生、传播和消散进行真实的数值模拟和密集的直接观测来完成。具体来说，将在苏必利尔湖进行大量观测，该湖在夏季以近惯性运动为主，潮汐可忽略不计，平均环流较弱，河流输入量很少，使其成为沿海海洋的理想实验室。观测结果将包括通过船基勘测和 Wirewalker 波浪动力系泊剖面仪对湍流进行大范围测量。三个传统系泊装置也将部署四年，扩展现有的时间序列，可用于识别极端事件和近惯性运动的长期趋势。该项目还包括对分析和数值模型的新颖分析，这将有助于收集和解释观测结果，并使苏必利尔湖的结果能够利用历史风、分层和测深数据扩展到整个沿海海洋。