Collaborative Research: Frontogenesis and Fine-Sediment Trapping in a Highly Stratified Estuary

智力优点：将在康涅狄格河河口进行河口锋生和沉积物截留在一个高度分层的河口的实地和模拟研究。河口锋生是河口水动力学和泥沙输运的一个基本机制，但对河口锋生的认识还不多。河口的锋面是任何海洋环境中观测到的最强锋面之一，产生强烈的局部密度梯度，层化、底应力和湍流的突然转变，强烈的垂直速度和强烈的沉积物截留。导致沉积物截留的过程取决于相同的物理变量，并发生在相同的尺度上，作为那些生产河口锋，河口锋和相关的沉积物截留的动力学的跨学科研究提供了强大的动力。康涅狄格河河口是现场-一个充满活力的制度与强烈的和高度依赖于时间的前和短暂的捕获细粒sediment.The观测计划将包括测量的锋面结构，因为它在潮汐和季节的时间尺度变化，以及密集，高分辨率的测量与固定和船上安装的仪器，以获得前所未有的空间和时间分辨率的物理制度。同时，将用光学和声学方法对悬浮泥沙浓度和特性进行量化，并进行广泛的实验室和实地校准工作。水柱观测将与河床沉积物特征描述相结合，以解决沉积物通量收敛、短暂沉积以及可再悬浮沉积物的时空变化之间的相互作用。观测结果将与高分辨率的水动力和泥沙输运数值模式相结合，以帮助解释观测结果，并研究导致锋生和相关泥沙截留的主要物理过程的细节。这项研究将全面研究河口锋生，将当前准稳态水力学的理论理解与部分混合河口的动力学相联系，定量和参数化锋生及其对整个河口制度的影响。通过高分辨率测量和建模的结合，研究小组将对沉积物捕获机制进行严格的检查，特别是在河口前缘和相关的短暂沉积物产生的强烈但高度依赖于时间的收敛的背景下。这项研究将解决这些水动力和沉积物输运过程的敏感性，在河口强迫条件的变化，根据所观察到的强迫和模型的敏感性研究的变化。模式敏感性研究还将用于确定锋面辐合过程是否可以解释河口形态的长期演变以及强迫变量变化对整个河口状况的潜在影响。这项研究将导致理解和改进河口锋面生成的预测，以及锋面对细泥沙和相关泥沙的命运和输运的影响。污染物。这些发现将应用于世界各地人口稠密，工业化和其他人类影响的河口的建模和管理。该项目包括实施新的教育内容：为来自国际河口研究界的研究生提供高级实地方法的短期课程，以及将与研究生实地课程相结合的本科实地研究课程。该项目还将支持两名研究生的论文工作。

Intellectual merit: A field and modeling study of estuarine frontogenesis and sediment trapping in a highly-stratified estuary will be conducted in the Connecticut River estuary. Frontogenesis in estuaries is poorly understood, yet it is a fundamental mechanism influencing many aspects of estuarine hydrodynamics and sediment transport. The fronts in estuaries are among the strongest observed in any marine environment, producing intense, localized density gradients, abrupt transitions in stratification, bottom stress, and turbulence, strong vertical velocities and intense sediment trapping. The processes that lead to sediment trapping depend on the same physical variables and occur at the same scales as those producing estuarine fronts, providing a strong motivation for an interdisciplinary study of the dynamics of estuarine fronts and associated sediment trapping. The Connecticut River estuary is the field site - an energetic regime with intense and highly time-dependent fronts and ephemeral trapping of fine-grained sediment.The observational program will include measurements of the frontal structure as it varies at tidal and seasonal timescales, as well as intensive, high-resolution measurements with fixed and ship-mounted instruments to obtain unprecedented spatial and temporal resolution of the physical regime. Simultaneously, suspended-sediment concentrations and properties with optical and acoustic methods will be quantified and subjected to an extensive laboratory and field calibration effort. The water-column observations will be coupled with bed-sediment characterization to address interactions among sediment flux convergence, ephemeral deposition, and spatially and temporally varying availability of resuspendable sediment. Observational measurements will be paired with a high-resolution numerical model of the hydrodynamics and sediment transport to help interpret the observations and to investigate the details of the dominant physical processes leading to frontogenesis and associated sediment trapping.The study will provide a comprehensive examination of estuarine frontogenesis, linking current theoretical understanding of quasi-steady hydraulics with the dynamics of partially-mixed estuaries in order to understand, quantify and parameterize frontogenesis and its influence on the overall estuarine regime. Through the combination of high-resolution measurements and modeling, the research team will perform a rigorous examination of the mechanisms of sediment trapping, particularly in context with the strong but highly time-dependent convergence resulting from estuarine fronts and the associated, ephemeral deposits of fine-grained sediment. The study will address the sensitivity of these hydrodynamic and sediment-transport processes to variations in estuarine forcing conditions, based both on the observed variation of forcing and model sensitivity studies. Model sensitivity studies will also be used to determine whether frontal convergence processes may explain the long-term evolution of estuarine morphology and the potential implications of shifts in forcing variables on the overall estuarine regime.Broader impacts: This study will lead to the understanding and improved prediction of the generation of fronts in estuaries and the influence of fronts on the fate and transport of fine sediment and associated contaminants. These findings will have application to the modeling and management of the heavily populated, industrialized and otherwise human-impacted estuaries around the world. This project includes implementation of new educational components: a short-course in advanced field methods for graduate students from across the international estuarine research community, and an undergraduate field research class that will be coupled to the graduate-level field class. The project will also support the thesis work of two graduate students.