Physics Linking Shelf Circulation to Estuarine Inflow

控制从沿海海洋流入河口或峡湾的水流来源的物理将利用理论和理想化的数值实验进行探索。具体目标是对水源的取水深度和取水的地理区域进行理论预测。这两个性质将被表示为控制环境变量的函数。参数空间将跨越各种各样的系统，从缓慢倾斜的大陆架上的浅海岸平原河口，到毗邻大陆架穿越峡谷的深峡湾。这项研究将告诉数值建模者，为了成功地预测流入河口的水的特性，陆架上必须包含哪些物理特性。这将使未来对由于沿海海洋水性质变化而导致的河口生物地球化学功能变化的预测得到改进。首席研究员和一名研究生将把拟议的研究结果直接与他们所在地区的利益相关者联系起来，并将结果传达给其他地区致力于实现预期社会成果的科学家。部分理论框架已经存在，这是基于之前对沿海上升流、峡谷、河流羽流和河口交换流的广泛研究。然而，在流入河口之前，陆架上的流入动力学仍然相对未被探索，与收集到的河流羽流相比，观测证据要少得多。两层流的早期解析解将是一个关键的起点。我们将进行理想化的数值实验来检验这组解的假设力平衡和流入路径。数值实验中的力平衡将使用三种方法进行分析：(i)沿流入粒子轨迹的拉格朗日动量预算，（ii）回溯时间的粒子跟踪，以有效地确定流入路径，以及（iii）密度（盐度）类的平均，以将纯平流输运与需要混合的输运分开。每一种都有优点和缺点，但结合起来，它们应该为理论的发展提供明确的指导，特别是从两层到连续分层的转变。在整个项目中，理论解释数值解的重要性质的能力将是对成功的检验。

The physics controlling the source of waters flowing from the coastal ocean into the mouth of an estuary or fjord will be explored using theory and idealized numerical experiments. The specific goals are to develop theoretical predictions of the depth from which source water is drawn and the geographical region from which it is drawn. These two properties will be expressed as functions of controlling environmental variables. The parameter space will span a wide variety of systems, from shallow coastal plain estuaries on a gently sloping shelf, to deep fjords adjoining a shelf-crossing canyon. This research will inform numerical modelers about what physics must be included on the shelf in order to successfully predict the properties of water flowing into an estuary. This will allow improved future predictions of the change in estuarine biogeochemical function due to changing water properties in the coastal ocean. The principal investigator and a grad student will connect the results of the proposed research directly with stakeholders in their own region, and will communicate results to scientists working toward desired societal outcomes in other regions.Parts of a theoretical framework already exist, based on extensive previous work on coastal upwelling, canyons, river plumes, and the estuarine exchange flow. However the dynamics of the inflow on the shelf before it reaches the estuary remain relatively unexplored, with substantially less observational evidence than has been gathered for river plumes. Early analytical solutions for two-layer flow will be a key starting point. Idealized numerical experiments will be conducted to test the assumed force balance and inflow paths of this set of solutions. Force balances in the numerical experiments will be analyzed using three methods: (i) Lagrangian momentum budgets along inflow particle tracks, (ii) backward-in-time particle tracking to efficiently determine inflow pathways, and (iii) averaging in density (salinity) classes to separate purely advective transport from that requiring mixing. Each offers advantages and drawbacks, but in combination they should provide clear guidance for advancing the theory, particularly moving from two layers to continuous stratification. Throughout the project the ability of a theory to explain important properties of the numerical solutions will be the test of success.