Collaborative Research: Interaction Between Plumes and Surface Waves from the Surf Zone to the Inner-Shelf

河流在向沿海海洋输送陆源物质（如沉积物、污染物）和淡水方面发挥重要作用，后者影响沿海环流。然而，近岸波浪和波浪破碎在羽流混合、运输和沿海岸线的最终命运中的作用尚不清楚。为了解决这一知识差距，该项目使用测量和数值模型相结合的方法来确定沿海海洋中浮力河羽水的命运。两个实地实验的观测结果将测量河流羽流在沿海海洋中的扩散和混合。这些实地地点的实际模拟与理想的数值模拟相结合，将使实验能够跨越广泛的参数空间，以便与各种海岸线上不同类型的河流相关。这项工作将提高对河流水混合和沿海海洋命运的了解，这对于量化沉积物、污染物、幼虫和近岸其他重要物质的扩散至关重要。因此，这项工作将有助于确定与减轻不同条件下沿海水质差造成的风险相关的空间和时间尺度，改进沿海水质预测并减少人类接触受污染的水。本研究将提高对小开尔文数、小-中等流量河羽在深度受限表面波存在下的动力学认识。先前的研究表明，波浪对羽流结构和混合有重要的影响，但在跨河流流量和跨冲浪带/内陆架区域的波浪/羽流相互作用的理解方面仍然存在重大的知识空白。这些知识差距限制了我们预测小河的最终命运及其携带的物质的能力，这些物质与沿海污染、幼虫运输等有关。初步模拟表明，波浪驱动的羽流变化显著，包括冲浪带内沿岸扩散增强和向内大陆架输出的淡水减少。一套理想的耦合海洋环流和波浪传播模型模拟了不同的河流流量、波浪高度、波浪方向、潮汐阶段和科里奥利强迫，将为探索波浪/羽流相互作用提供参数空间。理想化研究的结果将由现有研究地点（现有观察和实际模型输出）和新的补充研究地点得出的结论加以补充。新研究地点的观测活动和现实模拟旨在捕捉在现有地点未捕获的缺失参数空间和羽流度量。最后，将对理想模型和现实模型以及观测数据集进行综合分析，以解决四个关键假设。最终，本研究将：(1)确定在冲浪带捕获羽流水的物理机制；(2)表征河流动量通量与波浪动量通量对羽流范围的作用；(3)确定在冲浪带捕获的淡水输出到内大陆架的途径；(4)在存在浮力梯度的深度有限波浪破碎区域测试现有的湍流闭合模型。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rivers play an important role in delivering land-derived material (e.g., sediment, contaminants) and freshwater to the coastal ocean, the latter impacting coastal circulation. Yet the role of near-shore waves and wave breaking in plume mixing, transport, and ultimate fate along the coastline is not yet understood. To address this knowledge gap, this project uses a combination of measurements and numerical models to determine the fate of buoyant river plume water in the coastal ocean. Observations from two field experiments will measure river plume spreading and mixing in the coastal ocean. Realistic simulations of these field sites combined with idealized numerical simulations will allow the experiment to span a broad range of parameter space in order to be relevant to different types of rivers across a variety of coastlines. The improved understanding of river water mixing and fate in the coastal ocean that will result from the work is crucial to quantifying the spreading of sediment, pollutants, larvae, and other important material in the nearshore. Thus, this work will aid in identifying the spatial and temporal scales relevant to mitigating risks due to poor coastal water quality under varying conditions, improving coastal water quality predictions and reducing human exposure to contaminated waters. This study will improve the dynamical understanding of small Kelvin number, small-moderate discharge river plumes in the presence of depth-limited surface waves. Prior research has shown important wave impacts on plume structure and mixing, yet significant knowledge gaps remain in the understanding of wave/plume interactions across a range of river discharge and across the surf zone/inner-shelf region. These knowledge gaps limit our ability to predict the ultimate fate of small rivers and the material they carry with them, relevant to coastal pollution, larval transport, and more. Preliminary simulations suggest there is significant wave-driven plume modification including enhanced along-shore spreading within the surf zone and decreased freshwater export to the inner-shelf. A suite of idealized coupled ocean circulation and wave propagation model simulations for varying river discharge, wave height, wave direction, tidal stage, and Coriolis forcing will provide a parameter space to explore wave/plume interaction. The results from idealized studies will be augmented with conclusions from an existing study site (with existing observations and realistic model output) and a new complementary study site. The observational campaign and realistic simulations of the new study site are designed to capture the missing parameter space and plume metrics that were not captured at the existing site. Finally, combined analyses of the suite of idealized and realistic models and observational datasets will be done to address four key hypotheses. Ultimately this study will: (1) Determine the physical mechanisms that trap plume water within the surf zone, (2) characterize the role of riverine versus wave momentum fluxes on plume extent, (3) identify pathways through which freshwater trapped in the surf zone gets exported to the inner shelf, and (4) test existing turbulence closure models in the region of depth-limited wave breaking in the presence of buoyancy gradients.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.