The influence of shelf and offshore processes on the Mississippi River plume dynamics

智力优势：河流羽流动力学控制与河流排放相关的低盐度沃茨、营养物、沉积物和污染物的命运和运输。浮力驱动的迁移受到影响沿海环流的过程的影响，特别是大气通量、风应力和地形效应。这些相互作用已被广泛研究，在理想化和现实的设置。然而，大多数以前的研究都集中在河口排放宽或窄的大陆架，有简单的几何形状附近的河口和底坡，在跨岸方向。此外，河流羽流研究往往忽略了环境水流的影响，特别是与冲击大陆架的边界流有关的斜坡涡流，这种涡流可能会困住沃茨，将其从淡水源远距离输送，或促进滞留，导致沿海泛滥。边缘海的卫星数据和数值研究表明，地形和边界流，大量淡水排放附近的锋面和涡旋改变了传统的河流羽流行为，并改变了低盐度沃茨和来自陆地排水的相关物质的首选路径。拟议研究的主要目标是通过检查控制输送的过程来促进对河流羽流动力学的理解和命运的河流沃茨在复杂的地形，可变的风强迫和影响下的外部大陆架，斜坡和深层过程与边界流和相关的涡流场。该研究方法解决了概念部分和现实应用。过程导向实验将在一个现实的模型域设置进行，以分析地形和风力驱动的电流的密西西比河羽流的演变的作用。最近的进展，在数值研究的货架动态允许嵌套的高分辨率货架模型的层次结构的区域和大规模的模型，采用数据同化，涡流解决，从而使沿海到近海的相互作用的现实代表。这样的模型将采用在这项研究中的一个现实的测试案例应用程序的运输沃茨排放在密西西比河三角洲，世界上最大的河流之一，在复杂的地形和强大的环境流量相结合的地方。卫星产品将被用来确定密西西比沃茨和周围大陆架和深海流之间的相互作用的突出事件。将采用货架断裂附近的现场测量对模型结果进行定量评价。数值实验与现实，高频率强迫将执行详细研究特征事件的羽流/边界流相互作用，并分析控制跨边缘运输的机制。根据模型结果并对照未同化数据进行验证，对河流沃茨的分布、迁移和停留时间进行分析，将验证研究假设，并提高预测复杂环境中迁移路径的能力。大型河流排放量大，营养物质、沉积物和污染物含量高，对渔业、海洋健康、沿海开发和湿地保护;在遭受极端风暴条件和缺氧事件的地区，影响会扩大。沿海与近海相互作用所允许的与偏远生态系统的潜在连通性具有显著的科学和社会经济影响。这些关联使研究结果在教育和推广方面具有独特性，因为它们涉及学生、青年科学家和公众熟悉的问题。已经规划了广泛的相关活动，并将通过配套项目予以加强。PI和研究科学家都是女性，这是海洋学中代表性不足的群体。

Intellectual Merit: River plume dynamics control the fate and transport of low salinity waters, nutrients, sediments and pollutants associated with river discharge. The buoyancy driven transport is modified by processes that influence circulation in coastal seas, especially atmospheric fluxes, wind stress and topographic effects. These interactions have been studied extensively, in both idealized and realistic settings. However, most previous studies have concentrated on estuarine discharges on broad or narrow continental shelves that have simple geometry near the river mouth and bottom slopes in the cross-shore direction only. Furthermore, river plume studies have often neglected the effect of ambient currents, especially slope eddies associated with boundary flows impinging on the shelf, which can potentially either trap river waters and transport them great distances away from the freshwater source or promote retention that can lead to coastal inundation and flooding. Satellite data and numerical studies in marginal seas have revealed that topography and boundary currents, fronts and eddies in the vicinity of large freshwater discharges modify the conventional river plume behavior and alter the preferred pathways for low salinity waters and associated materials from land drainage.The broad goal of the proposed study is to advance the understanding of river plume dynamics by examining the processes that control the transport and fate of river waters in the presence of complex topography, variable wind forcing and under the influence of outer shelf, slope and deep processes associated with a boundary current and the related eddy field. The study methodology addresses both a conceptual part and a realistic application. Process oriented experiments will be performed in a realistic model domain setting to analyze the role of topography and wind-driven currents on the evolution of the Mississippi River plume. Recent advances in numerical studies of shelf dynamics allow the nesting of high resolution shelf models to a hierarchy of regional and large scale models that employ data assimilation, are eddy resolving and can thus enable the realistic representation of coastal to offshore interactions. Such a model will be employed in this study for a realistic test case application on the transport of waters discharged at the Mississippi River delta, one of the greatest world rivers, where a combination of complex topography and strong ambient flows are in place. Satellite products will by employed to identify prominent events of interaction between Mississippi waters and ambient shelf and deep sea flows. In-situ measurements near the shelf-break will be employed for a quantitative evaluation of model results. Numerical experiments with realistic, high frequency forcing will be executed to study characteristic events of plume/boundary current interaction in detail and analyze the mechanisms that control cross-marginal transport. Analysis of the distribution, transport and residence time of river waters based on model results and validated against unassimilated data will verify the study hypotheses and enhance the capability to predict transport pathways in complex settings.Broader Impacts: Large river discharges, due to their high volume and high content in nutrients, sediments and pollutants, play a prominent role in fisheries, ocean health, coastal development and wetland conservation; impacts are amplified at areas subject to extreme storm conditions and hypoxia events. The potential connectivity to remote ecosystems allowed by coastal to offshore interactions has pronounced scientific and socioeconomic impacts. These associations make the study results unique for education and outreach, as they relate to problems familiar to students, young scientists and the general public. Extensive relevant activities have already been planned and they will be strengthened by ancillary projects. The PI and the research scientist are women, an under-represented group in oceanography.