Circulation and Transport in the Hudson Shelf Valley

人们早就知道，大陆架上的海底峡谷和大陆坡上的海底峡谷为跨越大陆架和斜坡运输沉积物、营养物质和生物生物等物质提供了重要的途径。以前的研究几乎完全集中在更深的大陆斜坡峡谷上。与斜坡峡谷不同，较浅的陆架山谷受到表面和底部强迫的强烈影响，例如风和海浪，并且经常受到层结的巨大季节变化的影响。与斜坡峡谷不同的是，陆架峡谷延伸到浅水，那里的沉积物运输和生物过程特别活跃，因此有可能促进沉积物的跨陆架运输和营养物质上涌至近地表真光带。陆架峡谷在受人类活动影响最大的陆架地区与大陆斜坡和开阔海域的深水之间提供了直接的联系。研究目标以之前对斜坡峡谷的研究和对哈德逊大陆架山谷观测的初步分析为指导，哈德逊大陆架山谷是一个狭长的山谷，横跨中大西洋海湾的大陆架。哈德逊陆架河谷的沿谷(跨陆架)流主要由风力驱动，常达50厘米/S，比邻近大陆架上的跨陆架流大一个数量级，是跨陆架交换的重要通道。目标是定量地了解陆架山谷中的水流，特别是沿山谷的输送对风强迫的反应，这将与广泛的陆架山谷有关。该方法是一系列理想化数值模拟运行，旨在了解陆架山谷中水流的动态，并根据相关的无量纲参数量化流动的输送和垂直结构，并辅之以对哈德逊陆架谷现有观测结果的分析和对哈德逊陆架谷更真实的模拟，以评估理想化模型结果与现实陆架谷的相关性。对历史观测和数值模拟的分析将被用来解决与陆架山谷中的循环和运输以及谷流对陆架上的热、盐和养分平衡的贡献有关的基本科学问题。更广泛的影响：更好地理解陆架山谷中的循环和运输，特别是哈德逊陆架山谷，将为研究生物生产力和污染物/幼虫在陆架上的扩散提供物理背景。它还将有助于量化大陆架和斜率海之间的示踪剂和动量交换。该项目将通过全日制研究生的参与和本科生的参与产生教育影响。

It has long been known that submarine valleys over continental shelves and submarine canyons over continental slopes provide important pathways for transporting material such as sediment, nutrients and biological organisms across continental shelves and slopes. Previous studies have focused almost exclusively on deeper continental slope canyons. In contrast to slope canyons, shallower shelf valleys are strongly influenced by surface and bottom forcing, such as winds and waves, and often subject to large seasonal variations in stratification. Also in contrast to slope canyons, shelf valleys extend into shallow water, where sediment transport and biological processes are particularly active, and can therefore potentially facilitate cross-shelf transport of sediment and upwelling of nutrients to the near-surface euphotic zone. Shelf valleys provide a direct connection between the shelf region that is most strongly impacted by human activity and deep waters of the continental slope and open ocean.The research objectives are guided by previous studies of slope canyons and preliminary analysis of observations in Hudson Shelf Valley, a narrow and long valley that cuts across the continental shelf of the Middle Atlantic Bight. Along-valley (cross-shelf) flows in Hudson Shelf Valley are primarily wind-driven and often reach 50 cm/s, an order of magnitude larger than cross-shelf flows on the adjacent continental shelf, making it an important conduit for cross-shelf exchange. The goal is a quantitative understanding of the response of flows in shelf valleys, particularly the along-valley transport, to wind forcing that will be broadly relevant to a wide range of shelf valleys. The approach is a sequence of idealized numerical modeling runs aimed at understanding the dynamics and quantifying the transport and vertical structure of the flow in shelf valleys in terms of relevant non-dimensional parameters, and complemented by analysis of existing observations from Hudson Shelf Valley and more realistic simulations of Hudson Shelf Valley to evaluate the relevance of the idealized model results to a realistic shelf valley. Analysis of historical observations and numerical simulations will be used to address fundamental scientific questions concerning the circulation and transport in shelf valleys and the contribution of valley flows to heat, salt and nutrient balances on the shelf.Broader impacts: Better understanding of the circulation and transport in shelf valleys, and specifically Hudson Shelf Valley, will provide the physical background for studies of biological productivity and contaminant/larval dispersal on the shelf. It will also help quantify tracer and momentum exchanges between the continental shelf and the slope sea. The project will have educational impacts through the involvement of a full-time graduate student and participation by undergraduate students.