Collaborative Research: The Role of Wind in Estuarine Dynamics

智力价值：河口的物理运作取决于对其水域分层的力量和破坏这种分层的力量之间的竞争结果。60年来，破坏力一直被认为是潮汐，潮汐在崎岖的海底产生起伏不定的湍流。近年来，出现了一个新的参与者：风吹过河口。研究表明，风是一种有效的混合器，甚至可以使水柱脱层。最近，人们发现，这种混合不仅作为一维的垂直过程发生，而且还通过河口纵向和横向的密度结构应变而发生。这个项目的驱动假设是，除了驱动沿河口和跨河口的强环流外，它还可能是为典型的两层河口环流提供能量的混合的主要贡献者，至少在长取水和较弱环流的河口是这样。该项目旨在研究风在河口动力中的作用，并检验这些假说。为了研究这一作用，河口对外加风应力的反应必须以三维细节来描述，这是迄今为止尚未提供的细节。此外，必须清楚地识别这种反应，将其与相关的基础环流--较慢、较稳定的河口水流--分开。最后，这种描述必须适用于广泛的河口类别。要实现这一细节和理解，需要一个广泛而深入的观察和分析计划，并结合具有分离、解剖、整合和缩放多个环流和混合组件的能力的数值模式。切萨皮克湾的观测计划将涉及一系列密集的仪器，其中最新颖的是配备了测速仪和温盐记录器的高分辨率塔，可以直接测量应力分布。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、拖车采样方案，提供了密度结构的详细空间图，具有足够高的重复率，可以分辨一个潮汐周期的变化。与负责切萨皮克湾地区天气预报的气象学家合作，将有助于观察和分析这一复杂的、相互作用的系统。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提供的营养过剩。这些营养物质过度丰富了水域，并导致较低层的氧气下沉，这些下沉剥夺了生物资源利用这一宝贵栖息地的能力。在切萨皮克湾和长岛海湾等河口，这些凹陷可能会导致缺氧，甚至缺氧，即溶解氧的完全耗尽。为了恢复我国河口的健康，计划并正在实施耗资巨大的项目。这些管理项目如果要取得成功，就需要依赖于对河口环流物理的准确描述。此外，如果公众要提供必要的政治和经济支持，就需要向他们通报问题和为解决问题所做的努力。为此，该研究项目将参与教育和推广工作，特别是与COSEE海岸趋势计划和Horn Point实验室科学家-教育家计划的合作，并将有一名科学家兼教育家参与，他将领导一个本科生团队开发一个与切萨皮克湾死区河口环流(包括风混合)的作用有关的教学模块。最后，这项提议将为两名正在攻读博士学位的研究生和一名博士后研究员提供培训。

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.