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

合作研究：高度分层河口的锋生和细泥沙捕获

• 批准号: 1232928
• 负责人: Wayne Geyer
• 金额: $ 171.8万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1232928&HistoricalAwards=false
• 关键词: Collaborative; Research; Frontogenesis; Fine; Sediment

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.

智力价值：将在康涅狄格河口进行高分层河口的河口锋生和沉积物滞留的实地研究和模型研究。人们对河口锋生知之甚少，但它是影响河口水动力和沉积物输送许多方面的基本机制。河口锋面是所有海洋环境中观察到的最强烈的锋面之一，产生强烈的局部密度梯度、层结突然转变、底部应力和湍流、强大的垂直速度和强烈的沉积物滞留。导致沉积物滞留的过程取决于相同的物理变量，并以与河口前缘产生的过程相同的规模发生，这为河口前缘和相关沉积物滞留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地点 - 一个充满活力的区域，具有强烈且高度依赖时间的锋面和短暂捕获的细粒沉积物。观测计划将包括对锋面结构的测量，因为它随潮汐和季节时间尺度的变化而变化。使用固定和船载仪器进行密集、高分辨率的测量，以获得物理状况前所未有的空间和时间分辨率。同时，将通过光学和声学方法对悬浮沉积物浓度和特性进行量化，并进行广泛的实验室和现场校准工作。水柱观测将与床沉积物特征相结合，以解决沉积物通量收敛、短暂沉积以及可再悬浮沉积物的空间和时间变化可用性之间的相互作用。观测测量将与水动力和沉积物输送的高分辨率数值模型相结合，以帮助解释观测结果并调查导致锋生和相关沉积物捕获的主要物理过程的细节。该研究将对河口进行全面检查锋生，将当前对准稳态水力学的理论理解与部分混合河口的动力学联系起来，以理解、量化和参数化锋生及其对整个河口的影响政权。通过高分辨率测量和建模的结合，研究小组将对沉积物截留的机制进行严格的检查，特别是在河口前缘和相关的、短暂的细小沉积物造成的强烈但高度依赖时间的汇聚的背景下。 - 粒状沉积物。该研究将基于观测到的强迫变化和模型敏感性研究，解决这些水动力和沉积物输送过程对河口强迫条件变化的敏感性。模型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。更广泛的影响：这项研究将导致理解和改进预测河口锋面的产生以及锋面对细粒沉积物和相关污染物的命运和迁移的影响。这些发现将应用于世界各地人口稠密、工业化和其他受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：为国际河口研究界的研究生开设高级实地方法短期课程，以及将与研究生水平实地课程相结合的本科生实地研究课程。该项目还将支持两名研究生的论文工作。