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.

知识分子的优点：将在康涅狄格河河口进行高度分层河口的河口额造和沉积物捕获的领域和建模研究。河口中的额源是鲜为人知的，但它是影响河口流体动力和沉积物传输的许多方面的基本机制。河口中的前沿是任何海洋环境中观察到的最强的，它产生了强烈的局部密度梯度，分层，底部应力和湍流中的突然过渡，强烈的垂直速度和强烈的沉积物陷阱。导致沉积物陷阱的过程取决于相同的物理变量，并以与产生河口阵线的尺度相同的尺度发生，为跨学科研究河口阵线和相关沉积物诱捕的动力提供了强大的动力。康涅狄格河河口是现场地点 - 一个充满活力的局势，高度依赖时间的阵线和临时诱捕细粒沉积物。观察计划还将包括额叶结构的测量，因为它在潮汐和季节性时间表上也有所不同用固定和船舶安装的工具进行了深入的高分辨率测量，以获得实体制度的前所未有的空间和时间分辨率。同时，将量化和声学方法的悬浮液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。水柱观察结果将与床层表征相结合，以解决沉积物通量收敛，短暂沉积以及空间和时间上的相互作用之间的相互作用。观测测量将与流体动力和沉积物传输的高分辨率数值模型配对，以帮助解释观察结果，并研究导致额构和相关沉积物诱捕的主要物理过程的细节。该研究将对河口进行全面检查额叶生成，将准稳态液压药的当前理论理解与部分混合的河口的动力学联系起来，以便理解，量化和参数化额构及其对整体河口状态的影响。通过高分辨率测量和建模的组合，研究团队将严格检查沉积物诱捕机制，尤其是在河口阵线和相关的，罚款效果的强烈但高度依赖的融合的背景下 - 凝固的沉积物。这项研究将基于观察到的强迫差异和模型敏感性研究的变化，以解决这些流体动力和沉积物传输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额叶收敛过程是否可以解释河口形态的长期演变，以及转移在强迫变量对整体河口方向上的潜在影响。BROADER的影响：这项研究将导致理解和改善。预测河口中阵线的产生以及阵线对细沉积物和相关污染物的命运和运输的影响。这些发现将应用于人口稠密，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组成部分：来自国际河口研究社区的研究生的高级现场方法的短途课程，以及将与研究生级田间课程耦合的本科实地研究课程。该项目还将支持两位研究生的论文工作。