Dynamics of Well-Mixed Estuaries

淡水和盐水的混合是所有河口共同的基本过程。然而，混合良好的河口提出了一个有趣的悖论：混合如何发生，如果河口已经混合？该项目解决了这一矛盾，以及它如何涉及到更广泛的问题，河口分散在检查两个良好的混合河口，潮汐和淡水迫使相似，但高度对比的几何形状，一个狭窄的河口，一个单一的，统一的渠道和其他广泛的泻湖型河口复杂的，树枝状的通道网络。这项研究将解决这两个河口的耦合动量和盐平衡与密集的现场测量和高分辨率数值模拟相结合。影响混合良好的河口的混合和交换过程对近岸生物的生态和生活史、海岸环境的地球化学（包括碳收支）以及海岸海湾的形态动力学稳定性具有根本重要性。因此，这项研究的结果将为与海洋资源管理、碳固存和沿海可持续性有关的研究和管理提供信息。该项目将把很大一部分资源用于培养一名研究生。它还包括支持现场方法短期课程，为来自不同研究生课程的学生提供高级河口现场方法的培训。尽管部分混合和高度分层的河口动力学有一个坚实的理论框架，但混合良好的河口受到广泛的假设制度的影响，例如横向剪切分散，混沌平流和潮汐不对称引起的环流，但是没有这些不同过程的一致的合成或缩放。在狭窄的河口的情况下，混合被假设为导致从短暂的，情节性的限制事件定位在空间和时间。对于宽河口混合可能表现出一个更复杂的空间结构，主要是由横向锋在边缘的渠道和加强渠道交界处。本研究将探讨这些不同的机制，以及混合河口的强烈对比的几何形状的作用，使用观测和现实的模拟，以确定的过程，并使用模型的灵敏度研究与不同的几何参数的缩放不同的机制，并概括的结果。

Mixing between fresh and salt water is the fundamental process that is common to all estuaries. However well-mixed estuaries present an intriguing paradox: how can mixing occur if the estuary is already mixed? This project addresses that paradox and how it relates to the broader problem of estuarine dispersion in the examination of two well-mixed estuaries with similar tidal and freshwater forcing but highly contrasting geometries, one a narrow estuary with a single, uniform channel and the other a broad lagoon-type estuary with a complex, dendritic channel network. The study will address the coupled momentum and salt balances of these two estuaries with a combination of intensive field measurements and high-resolution numerical modeling. The mixing and exchange processes affecting well-mixed estuaries are fundamentally important to the ecology and life histories of nearshore organisms, to the biogeochemistry (including the carbon budget) of coastal environments, and to the morphodynamic stability of coastal embayments. The results of this study will thus inform research and management related to marine resource management, carbon sequestration, and coastal sustainability. The project will focus a large fraction of its resources on the training of a graduate student. It also includes support for a field methods short-course to provide training for students from different graduate programs in advanced estuarine field methods.Whereas the dynamics of partially mixed and highly stratified estuaries have a firm theoretical framework, well-mixed estuaries are subject to a wide range of hypothesized regimes, such as lateral shear dispersion, chaotic advection and tidal-asymmetry-induced circulation, but with no consistent synthesis or scaling of these different processes. In the case of the narrow estuary, mixing is hypothesized to result from brief, episodic restratification events localized in space and time. For the broad estuary mixing may exhibit a much more complex spatial structure, dominated by lateral fronts at the edges of the channels and intensified at channel junctions. This study will examine the roles of these different mechanisms in well mixed estuaries with strongly contrasting geometries, using observations and realistic simulations to identify the processes, and using model sensitivity studies with varying geometries to parameterize the scaling of the different mechanisms and to generalize the results.