Quantifying exchange between the surfzone and a stratified inner-shelf with dye tracer experiments

冲浪区和内陆架是迄今为止最具经济和生态重要性的海洋区域，对娱乐、食物和生态系统服务至关重要。尽管清洁的沿海水域对我们的经济和福祉很重要，但水质下降威胁着全世界的沿海生态系统和人类健康。健康的海岸是联邦机构、地方政府和非政府组织的重要优先事项。这项研究将使用染料释放实验来量化内陆架和冲浪区之间的交换，从而提高科学认识，从而能够准确预测圣地亚哥南湾从冲浪区通过内陆架的示踪剂(例如，幼虫、营养物质、病原体)交换。该区域是一个具有代表性的冲浪区和内陆架系统，允许项目成果得到普遍应用。该地区也是具有经济价值的海滩、国家公园、海洋保护区和国家河口研究保护区等资产的所在地。然而，它经常受到糟糕的水质的影响。这项研究将为当地管理人员和公民提供对区域示踪剂交换的洞察。研究人员将培训一名博士生，并通过斯克里普斯海洋研究所的本科生研究经验计划吸引本科生。此外，他们将为高中生主办三次SurfScience Teen会议，与服务不足的Kearny高中(加利福尼亚州圣地亚哥)的学生发展合作，并参加一年一度的Avanzamos会议，该会议向拉美年轻人介绍海洋科学。在这项研究期间，对观测和模型结果的分析将提高对冲浪区和分层内陆架之间示踪剂交换的物理过程的理解。通过关闭示踪剂质量平衡，可以准确地确定染料的命运。对观察到的和模拟的内架染料扩散系数的估计将被用来测试内架是“材料屏障”的程度。内陆架的横向扩散系数(假设小于冲浪区)可能与冲浪区的扩散系数相当或大于冲浪区的扩散系数，因为较大的内陆架涡长尺度可以补偿较弱的涡流速度。我们将研究大尺度层状内陆架相干结构的来源(相对于冲浪带产生的撕裂流)。远下游的海岸线染料观测和内陆架跨岸染料通量的测量将决定冲浪带稀释机制是或不是菲克的程度。观测和模型结果将被用来确定内陆架上层水柱分层是如何通过冲浪带喷出温暖水来设定的。最后，对分层内陆架上示踪剂的垂直混合进行了诊断。其他假设驱动的建模研究将在不同的层结、风和急流条件下执行

The surfzone and inner-shelf are by far the most economically and ecologically important ocean regions, vital for recreation, food, and ecosystem services. Despite the importance of clean coastal waters to our economy and well-being, declining water quality threatens coastal ecosystem and human health worldwide. Healthy coasts are a significant priority to federal agencies, local government, and non-governmental organizations. This study will use dye release experiments to quantify the exchange between the inner-shelf and the surfzone, improving scientific understanding and thus allowing for accurate prediction of tracer (e.g., larvae, nutrients, pathogens) exchange from the surfzone through the inner-shelf in the San Diego South Bay. This region is a representative surfzone and inner-shelf system, allowing project results to be applied generally. This region also is home to economically valuable beaches, State Parks, a Marine Protected Area, and a National Estuarine Research Reserve, among other assets. Yet, it is often impacted by poor water quality. This study will provide local managers and citizens insight into regional tracer exchange. The investigators will train a PhD student and engage undergraduates through the Scripps Institution of Oceanography Research Experience for Undergraduates program. Additionally, they will host three SurfScience Teen Conferences for high-school students, develop collaborations with students at the underserved Kearny High School (San Diego, California), and participate in the annual Avanzamos conference which introduces young Latinas to ocean science.During this study the analysis of observations and model results will improve the understanding of the physical processes governing tracer exchange between the surfzone and the stratified inner-shelf. By closing a tracer mass budget, dye fate can be accurately determined. Estimates of observed and modeled inner-shelf dye diffusivity will be used to test the extent to which the inner-shelf is a "material barrier". Inner-shelf lateral diffusivities (hypothesized to be smaller than the surfzone) may be comparable to or greater than surfzone diffusivities, as larger inner-shelf eddy length-scales may compensate for weaker eddy velocities. The source of stratified inner-shelf coherent structures with large length-scales (relative to surfzone generated rip currents) will be investigated. Shoreline dye observations far downstream and inner-shelf cross-shore dye flux measurements will determine the extent to which surfzone dilution mechanisms are or are not Fickian. The observations and model results will be used to determine how inner-shelf upper water column stratification is set by surfzone ejection of warm water. Lastly, the vertical mixing of tracer on the stratified inner-shelf will be diagnosed. Additional hypotheses driven modeling studies will be performed with varying stratification, wind, and rip current conditions