Collaborative Research: The Role of Wind in Estuarine Dynamics

智力价值：河口的物理作用取决于使其水域分层的力量和破坏这种分层的力量之间竞争的结果。60年来，破坏力一直被认为是潮汐，它通过在粗糙的海底上的潮起潮落产生湍流。近年来，一个新的参与者出现了：吹过河口的风。研究表明，风是一种有效的混合器，甚至可以使水柱分层。最近，人们发现这种混合不仅是一个一维的垂直过程，而且还通过河口纵向和横向的密度结构的应变而发生。本项目的驱动假说是，除了驱动河口沿岸和对岸的强环流外，它也可以是混合的主要贡献者，为经典的双层河口环流提供能量，至少在长时间取水和较弱环流的河口。该项目旨在研究风在河口动力学中的作用，并验证这些假设。为了检验这一作用，河口对施加风应力的反应必须以三维细节来描述，而这些细节迄今尚未提供。此外，这种反应必须明确识别，与潜在的流通利益分开？缓慢而稳定的河口水流。最后，这种描述必须可扩展到河口的大类。要获得这些细节和理解，需要广泛而深入的观察和分析程序，并结合能够分离、剖析、整合和缩放多个循环和混合组件的数值模型。切萨皮克湾的观测计划将涉及一系列密集的仪器，其中最新颖的是一个配备测速仪和温度-盐度记录仪的高分辨率塔，可以直接测量应力剖面。密集的浮标阵列将配备气象传感器，以测量风场的局部结构。最后，设计了一种多船、拖曳车辆采样方案，以足够高的重复率提供密度结构的详细空间图像，以解决潮汐周期的变化。与切萨皮克湾地区负责天气预报的气象学家合作，将有助于对这个复杂的互动系统进行观察和分析。更广泛的影响：河口的循环和封闭性质使其成为高产渔业，而渔业受到人类改变景观的影响的威胁。世界各地的河口都处于不同的退化状态，其主要原因是农业径流和城市污水输送的营养过剩。这些营养物质使水体过度富集，导致下层氧气下降，使生物资源无法利用这一宝贵的栖息地。在切萨皮克湾和长岛湾等河口，这些凹陷会导致缺氧甚至缺氧，即溶解氧的完全耗尽。为了恢复我国河口的健康，我们正在计划和实施耗资巨大的项目。这些管理计划如果要取得成功，就需要依赖于对河口环流物理特性的准确描述。此外，如果公众要提供必要的政治和经济支持，他们就需要了解问题和为解决问题所做的努力。为此，该研究项目将涉及教育和推广工作，特别是COSEE沿海趋势计划和角角实验室科学家-教育者计划，并将涉及一名科学家-教育者，他将领导一组本科生开发一个与切萨皮克湾死区河口环流（包括风混合）作用相关的教学模块。最后，本提案将提供2名攻读博士学位的研究生和1名博士后的培训。

Intellectual Merit: The physical workings of an estuary depend on the outcome of a contest between forces acting to stratify its waters, and forces acting to destroy this stratification. For six decades, the destructive force has been identified as the tides, which generate turbulence through ebb and flow over the rough bottom. In recent years, a new player has emerged: wind blowing over the estuary. Research has shown wind to be an effective mixer, even to the point of de-stratifying the water column. More recently, it has been found that this mixing takes place, not solely as a one-dimensional vertical process, but also through straining of the density structure in the longitudinal and lateral direction of the estuary. The driving hypothesis for this project is that, in addition to driving strong circulations along and across the estuary, it can also be a major contributor to the mixing providing the energy for the classical two-layer estuarine circulation, at least in estuaries with long fetches and weaker circulation. This project has been designed to investigate the role of wind in estuarine dynamics and to test these hypotheses. In order to examine this role, the response of the estuary to an applied wind stress must be described in three-dimensional detail, detail that has not been provided heretofore. In addition, this response must be clearly identified, separate from the underlying circulation of interest?the slower, steadier estuarine flow. Finally, this description must be scalable to the broad class of estuaries. Achieving this detail and understanding requires an extensive and intensive program of observation and analysis in combination with numerical models that have the ability to separate, dissect, integrate, and scale the multiple circulation and mixing components. The observational program in the Chesapeake Bay will involve an intensive array of instrumentation, the most novel of which is a high-resolution tower equipped with velocimeters and temperature-salinity recorders that will enable direct measurements of the stress profile. A dense array of buoys will be instrumented with meteorological sensors to measure local structure in the wind field. Finally, a scheme of multi-ship, towed-vehicle sampling is designed to provide detailed spatial pictures of the density structure with a sufficiently high repetition rate to resolve changes over a tidal cycle. A partnership with the meteorologists responsible for weather forecasting in the Chesapeake Bay region will aid both the observation and analysis of this complex, interactive system.Broader Impacts: The circulation and enclosed nature of estuaries make them highly productive fisheries, fisheries threatened by the effects of human alteration of the landscape. Estuaries worldwide are in various states of degradation, the chief cause of which is excess nutrients delivered from agricultural runoff and municipal sewage. These nutrients over-enrich the waters and lead to oxygen sags in the lower layers, sags that deprive living resources of the ability to use this valuable habitat. In estuaries such as Chesapeake Bay and Long Island Sound, these sags can proceed to hypoxia and even anoxia, the total depletion of dissolved oxygen. Costly programs are planned and underway to restore the health of our nation's estuaries. These management programs will need to rely on an accurate description of the physics of estuarine circulation if they are to be successful. In addition, the public will need to be informed of both the problem and the efforts toward solutions if they are to provide the political and economic support necessary. To that end, this research project will engage with education and outreach efforts, especially with the COSEE Coastal Trends program and with the Horn Point Laboratory Scientist-Educator Program, and will involve a scientist-educator, who will head a team of undergraduates to develop a teaching module related to the role of estuarine circulation (including wind mixing) in the Chesapeake Bay's Dead Zone. Finally, this proposal will provide training to two graduate students pursuing PhD degrees and a Postdoctoral fellow.