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.

封闭海洋盆地中正压潮汐的行为是很好理解的：在平面图中，盆地模式似乎以开尔文波的形式围绕盆地外围旋转，在北半球以逆时针方向旋转。该项目探讨了耦合斜压响应（波长远小于表面潮汐的内部盆地模式）是否可以解释大陆架上观测到的大型内潮汐。在存在任何地形变化的情况下，正压模式和斜压模式是耦合的，潮汐产生潜力可以产生大幅度的内盆模式和正压模式。由于斜压参数（密度异常和层结结构）随时间变化，斜压响应预计不会与潮汐产生潜力锁定在恒定相位，正压模式也是如此。尽管如此，在比潮汐周期更长的时间内，仍会出现缓慢调节的响应。内潮观测表明存在沿海岸的能量通量，并且由于水平速度矢量的旋转方向随深度的变化而变化，因此变量（速度、等温线位移）不符合简单的一型内波。然而，这种行为与浅滩深度上的斜压摩擦开尔文波一致。本研究将结合理论分析、理想化和现实模拟以及对先前收集的数据的分析，以研究沿海岸传播的内潮的产生和传播。理论技术将用于研究分层旋转盆地中沿大陆架对盆地规模正压潮汐强迫的斜压响应。将使用理想化数值模拟来研究由正压开尔文波与沿陆架测深变化相互作用产生的沿海岸传播内潮的结构。将量化正压到斜压能量转换对陆架宽度、层结、正压潮汐幅度和测深变化幅度的敏感性。将对美国西海岸陆架和斜坡区域进行正压潮汐产生内潮的真实模拟，以研究正压潮汐斜压能量转换和沿海内潮传播的性质。还将分析先前现场实验的长期时间序列，以确定那里内潮汐的空间结构以及沿海传播的性质。智力价值。许多大陆架目前的变化主要是由内潮汐决定的。目前尚不清楚沿海结构和传播的性质。本研究旨在提供理想化和现实的框架，以了解内潮汐沿海岸的捕获和传播。更广泛的影响。这项研究将支持俄勒冈州纽波特哈特菲尔德海洋科学中心游客中心 (HMSVC) 的永久展览和相关课程的开发。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、数值方法和现场数据分析技术的培训。内波和潮汐引起的沿海水域环流目前是加利福尼亚州和墨西哥太平洋沿岸关注的焦点。该项目还将使 PI 能够继续与墨西哥同事合作，设计墨西哥海岸内潮汐、内波和跨岸通量的观测研究。