Collaborative Research: Investigating Tidal Influences on Subtidal Estuary-Coast Exchange Using Observations and Numerical Simulations

该项目将调查潮汐对潮下动量动力学的影响以及受旋转影响的分层河口系统与沿海海洋之间界面处的交换。潮汐过程的突出挑战了传统的观点，即循环和交换是由重力循环。重点是识别剩余流产生的三种潮汐机制的重要性和性质：（a）轴向流垂直剪切和垂直涡动粘性之间的潮汐相关，与垂直剪切轴向潮流引起的轴向密度梯度应变有关;（B）横向剪切轴向潮流引起的轴向密度梯度差平流的涨落差异引起的潮汐平均次级环流;以及（c）由于轴向和横向潮流之间的相关性中的横向结构而引起的横向潮汐校正。将使用观测和数值模拟研究每种机制的潮下轴向动量方程中出现的诊断项。该网站是东部长岛湾（LIS），一个复杂的系统，但通常是广泛的，深河口的代表。将利用一套广泛的存档观测资料，包括几年来每天8次的基于渡船的声学多普勒海流剖面仪（ADCP）断面、系泊CTD剖面仪的水文模型时间序列以及过去约15年来的全年双周/月度CTD调查。新的实地工作包括额外两年的渡轮采样，以及潮汐过程识别所需的小型船舶拖曳波荡器/ADCP调查。这些调查将表征三维空间结构和湍流，剪切和分层的潮汐周期，从而填补了公认的需要，以促进对河口物理学的理解。数值模拟强调现实的强迫函数和湍流参数化和系数值的校准，以便捕获测量的速度剪切，分层和湍流的总观测特征（横向和垂直结构;潮汐周期的振幅和相位）。面向过程运行的现实配置的模型将被用来调查潮汐机制的作用。标量通量和传输途径将使用欧拉和拉格朗日分析方法的模式进行调查。河口海岸交换的理解有应用于水质管理。研究结果将与研究地点的决策者有关，这是一个受到周围沿海人口严重影响的城市河口。一个现有的面向公众的教育显示器，在渡轮的乘客区作为一个平台，为新的观察，将进行评估和重新设计的合作与URI海洋项目办公室和部门。环境与自然资源经济学。该展览提高了人们对河口物理海洋学及其与水质关系的认识，每年约有30万渡轮乘客。另外两年的速度和水文地理网格数据产品将张贴在渡轮项目网站（www.gso.uri.edu/foster）上。一名URI本科生和一名康涅狄格大学研究生将接受培训。研究结果将纳入康涅狄格大学本科和研究生课程的海洋学课程。

The project will investigate tidal influences on sub-tidal momentum dynamics and exchange at the interface between a rotation-influenced, stratified estuarine system and the coastal ocean. Prominence of tidal processes challenges the conventional view that circulation and exchange are dominated by gravitational circulation. Emphasis is on discerning the importance and nature of three tidal mechanisms for residual flow generation: (a) tidal correlations between axial current vertical shear and vertical eddy viscosity, associated with strain of the axial density gradient by vertically sheared axial tidal currents; (b) tidal-mean secondary circulation from ebb-flood differences in differential advection of the axial density gradient by laterally sheared axial tidal flow; and (c) lateral tidal rectification due to lateral structure in correlations between axial and lateral tidal currents. Diagnostic terms that appear in the sub-tidal axial momentum equation for each mechanism will be investigated using observations and numerical simulations. The site is eastern Long Island Sound (LIS), a complex system, but one that is generally representative of wide, deep estuaries. An extensive suite of archived observations will be exploited, including several years of 8-times daily ferry-based acoustic Doppler current profiler (ADCP) transects, time series of hydrographic casts from moored CTD profilers, and year-round biweekly/monthly CTD surveys over the past ~15 years. New fieldwork includes two additional years of ferry sampling, and small vessel towed-undulator/ADCP surveys needed for tidal process identification. The surveys will characterize the three-dimensional spatial structure and tidal cycles of turbulence, shear, and stratification, so filling a recognized need to advance understanding of estuarine physics. Numerical modeling emphasizes realistic forcing functions and calibration of turbulence parameterization and coefficient values such that gross observed features (lateral and vertical structure; amplitudes and phases of tidal cycles) of measured velocity shear, stratification, and turbulence are captured. Process-oriented runs of the realistically configured model will be used to investigate the roles of tidal mechanisms. Scalar fluxes and transport pathways will be investigated with the model using both Eulerian and Lagrangian analysis methods. Understanding of estuary-coast exchange has applications to water quality management. Findings will be relevant to decision makers at the study site, an urban estuary heavily impacted by surrounding coastal populations. An existing public-oriented educational display, in the passenger area of the ferry serving as one platform for new observations, will be assessed and redesigned by collaboration with URI Office of Marine Programs and Dept. of Environmental and Natural Resource Economics. The display raises awareness of estuarine physical oceanography, and its connection to water quality, among ~300,000 ferry riders per year. Two additional years of velocity and hydrographical grid data products will be posted at the ferry project website (www.gso.uri.edu/foster). A URI undergraduate and a University of Connecticut graduate student will be trained. Results will be incorporated in University of Connecticut oceanography courses for undergraduate and graduate classes.