Collaborative Research: An Observational and Modeling Study of the Physical Processes Driving Exchanges between the Shelf and the Deep Ocean At Cape Hatteras

美国东海岸最近的异常情况极大地证明了了解控制哈特拉斯角附近北大西洋环流汇合处陆架-深海交换的动力学的重要性。非典型的墨西哥湾流位置、海气热通量、极端的海洋温度和海平面上升是大气和海洋强迫发生更大变化的潜在先兆。由于对目前的动力学理解不完整，对陆架-深海交换的影响尚不清楚。目前，由于石油和天然气勘探正在规划之中，预测能力的发展尤其重要。通过该项目获得的对陆架-深海交换的了解将适用于陆架和盆地规模洋流汇聚的其他区域，并可提高我们预测沿海海洋在未来几十年对气候变化的反应的能力。除了尺度和海洋区域之间的实际相互作用外，哈特拉斯角出口的陆架水与全球碳收支的相关性可能很大，由于生物生态系统调节碳收支，碳收支随季节和水量而变化，因此很难量化。生态系统和出口过程都可能在预测的气候变化下发生变化，因此了解出口过程具有广泛的生物地球化学重要性。将与生物地球化学家和生态学家合作，利用这些数据来研究这一生物多样性很高的地区的生态系统，这一地区是许多重要商业物种的家园。通过该项目获得的见解也将改善污染物泄漏的缓解。外展和教育努力包括一个公开展览和演讲，参加科学巡游的机会和参加女工程师协会“Girls Engineering It！Day”，这是一个为6-12年级女孩举办的为期一天的活动，以及伍德霍尔海洋研究所为代表不足群体的本科生举办的暑期项目。该项目将支持两名早期职业科学家，培养一名博士后研究员和四名研究生，并为本科生提供自主滑翔机操作的实践经验。副热带和亚极地海洋环流边界的特点是西部边界流汇聚，并在邻近的陆架和斜坡水域汇聚。合在一起，它们导致大量陆架水净出口到深海，以及复杂的双向陆架-深海交换，以应对典型的中纬度西部洋缘的强烈强迫。这种动态地点的陆架-深海交换过程仍然知之甚少，部分原因是解决相关空间和时间尺度的广泛范围的技术挑战。通过调查参数空间的广泛季节范围所获得的理解将有助于探索陆架环流和陆架-开阔海洋交换可能如何由于区域和盆地规模的环流、水文和大气强迫的观测和预测的长期变化而演变。该项目将部署固定的、移动的和远程观测平台，并结合理想和现实的数值模拟来研究哈特拉斯角附近的交换过程。该采样阵列将在一个大插曲输出和交换区域提供具有前所未有的时间和空间分辨率的观测数据集。这些观测将用于确定主要的交换过程；将它们与观测到的强迫联系起来；确定强迫和陆架反应的范围；核实现实模式框架内的平行发展；并通过详细评估动量和涡度平衡，结合观测和验证的模式产品，确定因果关系。除了物理数据外，自动滑翔机还将收集与从大陆架输出到深海的生物地球化学性质直接相关的叶绿素荧光、氧饱和度和声学后向散射数据。这些非物理数据将被用作水团示踪剂，并以前所未有的分辨率描绘叶绿素-a和溶解氧的结构。

Recent unusual conditions along the U.S. East Coast have dramatically demonstrated the importance of understanding the dynamics controlling shelf-deep ocean exchange at the confluence of the North Atlantic gyres near Cape Hatteras. Atypical Gulf Stream position, air-sea heat flux, extremes in ocean temperature, and sea level rise are potential harbingers of larger shifts in atmospheric and oceanic forcing. Effects on shelf-deep ocean exchange are unknown due to incomplete dynamical understanding of the present. Development of predictive capacity is particularly relevant at this time, as oil and gas exploration is being planned. The understanding of shelf-deep ocean exchange gained through this project will be applicable to other regions where shelf and basin-scale currents converge and could improve our capacity to anticipate the response of the coastal ocean to climate change in the coming decades. In addition to the physical interactions between scales and oceanic regions, the relevance of exported shelf waters at Cape Hatteras to global carbon budgets may be large, and is difficult to quantify due to carbon budget mediation by biological ecosystems that vary with season and water mass. Both ecosystems and export processes may change under predicted climatic shifts, so understanding export processes has broad biogeochemical importance. Collaborations with biogeochemists and ecologists will be pursued to utilize the data to study ecosystems in this area of high biological diversity that is home to many commercially important species. Insights gained through the project will also improve mitigation of pollutant spills. The outreach and educational efforts include a public exhibit and talks, opportunities for joining science cruises and participation in the Society of Women Engineers "Girls Engineer It! Day", a daylong event for girls in grades 6-12, and the Wood Hole Oceanographic Institution's summer program for undergraduates from underrepresented groups. The project will support two early career scientists, train one postdoctoral researcher and four graduate students, and give undergraduate students hands-on experience in the operation of the autonomous gliders.Subtropical and subpolar oceanic gyre boundaries are characterized by confluent western boundary currents and convergence in the adjacent shelf and slope waters. Together, they lead to large net export of shelf waters to the deep ocean, and complex, bidirectional shelf-deep ocean exchange, in response to strong forcing typical of mid-latitude western ocean margins. Shelf-deep ocean exchange processes at such dynamic sites remain poorly understood, due in part to the technical challenge of resolving broad ranges of relevant spatial and temporal scales. The understanding gained by investigating the wide seasonal range of parameter space will facilitate exploration of how shelf circulation and shelf-open ocean exchange may evolve due to observed and projected long-term shifts in regional and basin-scale circulation, hydrography, and atmospheric forcing. This project will deploy fixed, mobile, and remote observational platforms in combination with idealized and realistic numerical simulations to investigate exchange processes near Cape Hatteras. The sampling array will provide an observational data set with unprecedented temporal and spatial resolution in a region of large episodic export and exchange. These observations will be used to identify dominant exchange processes; correlate them with observed forcing; define ranges of forcing and shelf response; verify parallel developments within the realistic model framework; and establish causation through detailed assessment of momentum and vorticity balances, integrating observational and validated model products. In addition to physical data, the autonomous gliders will also collect chlorophyll fluorescence, oxygen saturation, and acoustic backscatter data that are of direct relevance to biogeochemical properties exported from the shelf to the deep ocean. These non-physical data will be used as water mass tracers and to portray the structure of the chlorophyll-a and dissolved oxygen at unprecedented resolution.