Circulation and Exchange Across the Inner Shelf - The Importance of Surface Gravity Waves and Cross-shelf Wind Stress

沿海海洋学中最重要的问题之一是确定跨陆架交换的机制和途径(例如，海洋科学，2001年)。内陆架上的跨陆架和垂直交换对广泛的跨学科过程产生重大影响，包括在沿海上升流期间向真光带提供营养物质，在生物生命周期的不同阶段在河口或潮间水域和中间陆架之间的生物移动，沉积物的离岸移动，污染物的离岸扩散，以及诸如溢油到海滩上的污染物沉积。尽管内陆架很重要，但负责整个内陆架交换的主要机制和相关的动态仍然不确定。很少有人试图弥合近岸冲浪区研究和陆架研究之间的差距，前者侧重于波浪驱动的过程，后者侧重于风力驱动的过程(见Lentz等人，2001年是一个例外)。因此，近岸模式一般集中在冲浪区，通常不考虑风强迫或层结，而陆架模式通常不包括波浪强迫(例如，Austin和Lentz 2002)。在这项研究中，伍兹霍尔海洋研究所的研究人员将研究是否表面重力波和跨陆架风应力迫使内陆架大部分地区的跨陆架循环和交换。为了做到这一点，科学家将分析从海岸天文台和以前的内陆架研究中获得的现有观测结果。玛莎葡萄园岛海岸观测站(MVCO)将部署一个三元素跨陆架阵列，以获取密度和海流剖面，以确定层结对跨陆架环流的影响。应力分布的直接协方差估计将利用现有的来自MVCO的2赫兹ADCP数据的四年时间序列进行，并将开发一个简单的波浪驱动的跨陆架环流分析模型。最后，我们将使用一个具有湍流闭合方案的二维原始方程数值模式来研究层结和地面热通量对风和波浪驱动的环流的影响。这项工作的目标是对内陆架上风和浪驱动的环流达成动力学上的理解。此外，这项研究将通过在原始方程数值模式中提供经过观测检验的表面重力波强迫的参数化和应力观测来评估和改进现有的湍流闭合方案，从而加强沿海海洋界可用的三维数值模拟能力。

One of the most important problems in coastal oceanography is determining the mechanisms and pathways of cross-shelf exchange (e.g. Ocean Sciences 2001). Cross-shelf and vertical exchange over the inner shelf has a major impact on a wide range of interdisciplinary processes, including the supply of nutrients to the euphotic zone during coastal upwelling, the movement of organisms between estuarine or inter-tidal waters and the mid shelf during different stages of their life cycles, the on-offshore movement of sediment, the offshore dispersal of pollutants, and the deposition of contaminants such as oil spills onto beaches. Despite the importance of the inner shelf, the dominant mechanisms responsible for exchange across the inner shelf and the associated dynamics remain uncertain. There have been few attempts to bridge the gap between nearshore surfzone studies focusing on wave-driven processes and shelf studies focusing on wind-driven processes (see Lentz et al 2001 for an exception). Consequently, nearshore models generally focus on the surfzone and typically do not consider wind forcing or stratification, while shelf models generally do not include wave forcing (e.g. Austin and Lentz 2002). In this study, researchers at the Woods Hole Oceanographic Institution will examine whether or not the cross-shelf circulation and exchange over a substantial portion of the inner shelf is forced by surface gravity waves and cross-shelf wind stresses. To do so, the scientist will analyze existing observations from coastal observatories and previous inner-shelf studies. A three element cross-innershelf array at the Martha's Vineyard Coastal Observatory (MVCO) will be deployed to obtain density and current profiles to determine the impact of stratification on the cross-shelf circulation. Direct covariance estimates of stress profiles will be made using an existing four-year time series of 2-Hz ADCP data from the MVCO, and a simple analytic model of the wave-driven cross-shelf circulation will be developed. Finally, a two-dimensional primitive-equation numerical model with a turbulence closure scheme will be used to investigate the influence of stratification and surface heat flux on the wind- and wave-driven circulation. The goal of this work is to reach a dynamical understanding of the wind-and wave-driven circulation over the inner shelf. In addition, the research will enhance the three-dimensional numerical modeling capability available to the coastal oceanographic community by providing observationally tested parameterizations of surface-gravity-wave forcing in a primitive-equation numerical model and stress observations for evaluating and refining existing turbulence closure schemes.