Circulation and Transport in the Hudson Shelf Valley

人们早就知道，大陆架上的海底峡谷和陆坡上的海底峡谷为跨越大陆架和陆坡运输沉积物、营养物质和生物有机体等物质提供了重要途径。以前的研究几乎完全集中在更深的大陆斜坡峡谷上。与斜坡峡谷相比，较浅的陆架山谷受到地面和底部强迫的强烈影响，例如风和波浪，并且经常受到分层的大季节变化的影响。与斜坡峡谷相反，陆架山谷延伸到浅水，那里的沉积物运输和生物过程特别活跃，因此可能促进沉积物的跨陆架运输和营养物质上涌到近地表的泛光带。陆架山谷在受人类活动影响最强烈的陆架区域与大陆斜坡和开阔海洋的深水之间提供了直接联系。研究目标以先前对斜坡峡谷的研究和对哈德逊大陆架山谷的初步观测分析为指导。哈德逊大陆架山谷是一个狭长的山谷，横跨大西洋中部湾的大陆架。哈德逊大陆架山谷的沿谷（跨大陆架）流主要由风力驱动，通常达到50厘米/秒，比相邻大陆架上的跨大陆架流大一个数量级，使其成为跨大陆架交换的重要渠道。目标是定量了解陆架山谷中流动的响应，特别是沿着山谷的运输，对风强迫的反应，这将与广泛的陆架山谷广泛相关。该方法是一系列理想化的数值模拟运行，旨在根据相关的非量纲参数了解陆架谷内流动的动力学和量化运输和垂直结构，并辅以对哈德逊陆架谷现有观测数据的分析和更现实的哈德逊陆架谷模拟，以评估理想化模型结果与现实陆架谷的相关性。对历史观测的分析和数值模拟将用于解决有关陆架山谷的环流和运输以及山谷流动对陆架上的热、盐和营养平衡的贡献的基本科学问题。更广泛的影响：更好地了解陆架山谷，特别是哈德逊陆架山谷的环流和运输，将为研究陆架上的生物生产力和污染物/幼虫扩散提供物理背景。它还将有助于量化大陆架和斜坡海之间的示踪剂和动量交换。该项目将通过全日制研究生和本科生的参与对教育产生影响。

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.