Coastal Ocean Reynolds Stresses: Using New Methods with Long-Term Observations to Investigate Exchange and Evaluate Model Closures

在大陆架上，湍流在通过水柱分配动量方面起着主要作用。在表层和底层边界层重叠的内陆架，湍流动量通量(雷诺应力)的大小和垂直结构被认为对环流和交换具有控制性影响。沿海海洋中雷诺应力的垂直结构尚不为人所知，部分原因是很难对波浪环境中的应力做出公正的估计。最近开发的分析技术记录了解释波浪引起的偏差的方法，允许使用共同部署的声学多普勒海流剖面仪(ADCP)的速度剖面直接观测沿海海洋应力。这项工作建议使用这些方法来估计来自玛莎葡萄园岛海岸天文台(MVCO)长达10多年的速度剖面记录中存在的应力。估计的应力将与速度、水文和风观测一起被用来研究陆架内部过程如何相互作用，以确定由于陆架风、跨架风和表面重力波造成的跨架交换，并将这些过程引起的动量转移的变化与跨架交换的变化联系起来。这些估计将与在简单的一维和二维或复杂的三维数值模式模拟中针对类似强迫条件的常用湍流闭合模型的预测进行比较。智力价值：对湍流应力分布的现场观测，传统上是动量方程中最难获得的项，对我们解释和预测沿海海洋动力学的能力至关重要。使用长期数据集，这项工作将分离风或波浪强迫对雷诺应力的增量影响，检查跨陆架环流对应力的依赖性。将这些观测结果与数值模型的预测进行比较，将为评估闭合方法提供一个强大的新工具，从而能够更准确地预测在没有这种测量方法时，导致压力的过程如何相互作用来驱动循环。分析的主要数据产品，即根据MVCO的长期速度数据集估计的应力分布，将被存档并提供给天文台的网站，因此可以作为社区数据产品用于未来的研究。更广泛的影响：控制水团和营养物质跨大陆架交换的机制控制沿海海洋的生产力以及浮游幼虫和污染物的扩散或保留。湍流应力的更多知识及其在评估模式参数化中的使用，潜在地提供了比以前可能的对内陆架和跨陆架交换的动力学更精确的理解，从而能够以更高的精度研究和模拟依赖于交换的过程。结果将通过教学和正在进行的推广计划直接传播到课堂上。

Over the continental shelf, turbulence plays a primary role in distributing momentum through the water column. In the inner shelf, where surface and bottom boundary layers overlap, the magnitude and vertical structure of turbulent momentum flux (Reynolds stress) is thought to have a controlling influence on the circulation and exchange. The vertical structure of Reynolds stress in the coastal ocean is not well known, due in part to the difficulty in making unbiased estimates of stress in wavy environments. Recently developed analysis techniques have documented ways to account for wave-induced biases, allowing direct observations of coastal ocean stresses using the velocity profiles of commonly-deployed acoustic Doppler current profilers (ADCPs). This work proposes to use these methods to estimate the stresses present in a more than 10 year-long record of velocity profiles from the Martha's Vineyard Coastal Observatory (MVCO). Estimated stresses will be utilized, along with velocity, hydrographic, and wind observations, to examine how inner-shelf processes interact to determine the across-shelf exchange due to along-shelf winds, across-shelf winds, and surface gravity waves and relate variations in momentum transfer due to these processes to variations in across-shelf exchange. These estimates will be compared to predictions using common turbulence closure models for similar forcing conditions in both simple one- and two-dimensional or complex three-dimensional numerical model simulations. Intellectual Merit: In situ observations of turbulent stress profiles, traditionally the least accessible term in the momentum equations, are central to our ability to explain and predict coastal ocean dynamics. Using the long-term dataset, this work will separate the incremental effects of wind or wave forcing on Reynolds stresses, examining the dependence of the across-shelf circulation on the stress. Comparing these observations to predictions from numerical models will provide a powerful new tool to evaluate closure methods, enabling more accurate predictions of how stress-causing processes interact to drive circulation when such measurements are not available. The primary data product of the analysis, stress profiles estimated from MVCO's long-term velocity dataset, will be archived and served on the Observatory's website, and therefore available as a community data product for future research. Broader Impacts: The mechanisms that control the across-shelf exchange of water masses and nutrients control the productivity of the coastal ocean as well as the dispersal or retention of planktonic larvae and pollutants. The additional knowledge of turbulent stresses and their use in evaluating model parameterizations offer, potentially, a more precise understanding of the dynamics of the inner shelf and across-shelf exchange then has previously been possible, allowing exchange-dependent processes to be studied and modeled with increased accuracy. Results will be disseminated directly into the classroom via teaching and ongoing outreach programs.