Collaborative Research: Along-coast structure and propagation of internal tides

合作研究：沿海结构与内潮汐传播

• 批准号: 1155799
• 负责人: James Lerczak
• 金额: $ 27.03万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2017-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1155799&HistoricalAwards=false
• 关键词: Collaborative; Research; Along; coast; structure

The behavior of the barotropic tide in a closed ocean basin is well understood: in plan view the basin modes appear to rotate around the periphery of the basin as Kelvin waves, in the counter- clockwise sense in the northern hemisphere. This project explores whether the coupled baroclinic response, internal basin modes of much smaller wavelength than the surface tide, can be responsible for the large internal tides that are observed on the continental shelf. In the presence of any topographic variability, the barotropic and baroclinic modes are coupled, and the tide generating potential can generate large amplitude internal basin modes as well as barotropic modes. Because the baroclinic parameters (density anomaly and stratification structure) vary in time, the baroclinic response is not expected to be locked in constant phase with the tide generating potential, as is the barotropic mode. Nonetheless there will be a response that is slowly modulated, over times that are longer than a tidal period. Observations of internal tides reveal that there exists an along-coast energy flux, and that the variables (velocities, isotherm displacements) do not conform to a simple mode one internal wave, because the sense of rotation of the horizontal velocity vector changes with depth. That behavior is however consistent with baroclinic frictional Kelvin waves over shoaling depth.This study will combine theoretical analyses, idealized and realistic simulations and analyses of previously collected data to study the generation and propagation of along-coast propagating internal tides. Theoretical techniques will be used to investigate baroclinic response along continental shelves to basin-scale barotropic tidal forcing in a stratified, rotating basin. Idealized numerical simulations will be used investigate the structure of along-coast propagating internal tides generated by barotropic Kelvin waves interacting with along-shelf bathymetric variations. The sensitivity of barotropic to baroclinic energy conversion to shelf width, stratification, amplitude of barotropic tide and amplitude of bathymetric variability will be quantified.Realistic simulations of internal tide generation by barotropic tides will be conducted for U.S. west coast shelf and slope domains to investigate barotropic to baroclinic energy conversion and the nature of along-coast internal tide propagation. Long-term time series from previous field experiments also will be analyzed to determine the spatial structure of internal tides there and the nature of along-coast propagation.Intellectual Merit. Current variability on many continental shelves is dominated by internal tides. The nature of along-coast structure and propagation is currently not known. This study aims to provide the idealized and realistic framework with which to understand along-coast trapping and propagation of internal tides.Broader Impacts. This study will support the development of a permanent exhibit and related curriculum at the Hatfield Marine Science Center?s Visitor Center (HMSVC) in Newport, OR. A graduate student at Scripps Institution of Oceanography will be supported by this study and will be trained in coastal physical oceanography, numerical methods, and in field data analysis techniques. The circulation induced in coastal waters by internal waves and tides are currently the focus of attention along the Pacific coast of California and Mexico. This project will also allow the PIs to continue their collaboration with Mexican colleagues in the design of an observational study of internal tides, internal waves and cross-shore fluxes off the Mexican coast.

正压潮汐在封闭海洋盆地中的行为是很好理解的：在平面图中，盆地模式看起来像开尔文波一样围绕盆地的外围旋转，在北方逆时针方向。该项目探讨了耦合斜压响应，比表面潮汐波长小得多的内部盆地模式，是否可以负责在大陆架上观察到的大型内部潮汐。在地形变率存在的情况下，正、斜压模态耦合，引潮力位能产生大振幅的内盆模态和正压模态。由于斜压参数（密度异常和层结结构）随时间变化，斜压响应预计不会像正压模态那样与潮汐生成势锁定在恒定相位。尽管如此，在比潮汐周期更长的时间内，会有一个缓慢调制的响应。内潮的观测表明，存在沿海岸的能量通量，并且变量（速度，等温线位移）不符合简单的模式1内波，因为水平速度矢量的旋转方向随深度而变化。本研究将结合联合收割机理论分析、理想化与现实化模拟以及先前所收集资料的分析，来研究沿岸传播内潮的产生与传播。理论技术将被用来调查斜压响应沿着大陆架盆地尺度正压潮汐强迫在分层，旋转盆地。将使用理想化的数值模拟研究正压开尔文波与沿大陆架水深变化相互作用产生的沿海岸传播的内潮的结构。正压-斜压能量转换对陆架宽度、层结、正压潮汐振幅和水深变率振幅的敏感性将被量化。正压潮汐产生内潮的真实模拟将在美国西海岸陆架和陆坡域进行，以研究正压-斜压能量转换和沿岸内潮传播的性质。还将分析以前实地实验的长期时间序列，以确定那里内潮的空间结构和沿岸传播的性质。许多大陆架的海流变化主要是由内潮所控制的。沿岸结构和传播的性质目前尚不清楚。本研究旨在提供一个理想化和现实的框架，以了解沿海捕获和内潮的传播。这项研究将支持在哈特菲尔德海洋科学中心的永久展览和相关课程的发展？位于俄勒冈州纽波特的游客中心（HMSVC）。斯克里普斯海洋学研究所的一名研究生将得到这项研究的支持，并将接受沿海物理海洋学、数值方法和实地数据分析技术方面的培训。内波和潮汐在沿海沃茨引起的环流是目前沿着加州和墨西哥太平洋沿岸关注的焦点。这一项目还将使项目研究员能够继续与墨西哥同事合作，设计一项关于墨西哥沿海内潮、内波和跨岸通量的观测研究。