Collaborative Research: Pathways and fate of freshwater near the southern tip of Greenland

该项目将调查格陵兰冰盖融化的淡水如何离开格陵兰岛最南端的告别角附近的沿海海洋。随着输送大陆架上大部分淡水的沿岸流到达好望角，强风强迫加上其相对于海岸线曲率的方向和复杂的水深测量，可能会将那里的水冲到近海。 该项目将部署漂流器和剖面浮标，在模拟环流的背景下进行解释，以调查这些大量淡水如何进入公海。先前的研究表明，这种输出的陆架水可能对大西洋经向翻转环流（AMOC），从而对全球气候产生潜在的影响。该项目将支持一名观察型年轻研究员的职业发展，将开发一个特定于该项目的网站，一名本科生暑期研究员将帮助分析数据，一名志愿本科生将参加一次研究巡航。这项工作将阐明高纬度陆架淡水如何影响大规模的海洋环流，并应适用于其他地区的浮力沿海流周围尖锐的测深转向。更广泛的相关性将包括解决融水可能会影响北大西洋春季水华的地方和方式，通过其供应的微量营养素和分层的亚极地北大西洋。目前融化的北极和格陵兰冰盖引入足够的淡水到亚极地北大西洋显着改变大西洋经向翻转环流，但是，这些水在何处以及如何离开陆架海洋，与边界流和副极地北大西洋的深海盆地相互作用，却没有受到很好的限制。该项目将使用联合观测和建模研究来探索告别角周围淡水的路径和命运，并确定驱动通量的强迫机制。2021年和2022年，将在格陵兰岛东南部大陆架沿着部署表面漂流器和快速剖面Argo浮标，以评估沿岸流的顺流、横流和垂直一致性。建模组件将播种一个高分辨率（约2公里的横向网格间距）的MITgcm的一年之久的运行与虚拟浮子在沿海流中遵循其路径周围的告别角，通过检查模型环流响应内部不稳定性和外部强迫，并量化所产生的模拟陆架盆地交换的补充。这项工作将提供第一个全面的研究，陆架盆地交换周围的告别角，一个过程中经常援引来解释北大西洋的variability.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This project will investigate how freshwater melt from the Greenland ice sheet exits the coastal ocean near Cape Farewell, the southernmost tip of Greenland. As the coastal current transporting much of the fresh water on the shelf reaches the Cape, the strong wind forcing combined with its orientation with respect to the coastline curvature and complex bathymetry may flush water offshore there. The project will deploy drifters and profiling floats, interpreted in the context of modeled circulation to investigate how this high volume freshwater may enter the open ocean. Prior studies have indicated the potential influence this exported shelf water may have on the Atlantic Meridional Overturning Circulation (AMOC), and hence global climate. The project will support the career development of an observational young investigator, a project-specific website will be developed, an undergraduate summer student fellow will help analyze the data, and a volunteer undergraduate student will participate in a research cruise. This work will clarify how shelf-derived fresh water at high latitudes can influence the large-scale ocean circulation, and should be applicable to other regions where buoyant coastal currents veer around sharp bathymetry. Broader relevance will include addressing where and how meltwater may affect the North Atlantic spring bloom through its supply of micronutrients and stratification of the subpolar North Atlantic.The current melting of the Arctic and the Greenland Ice Sheet introduces enough fresh water into the subpolar North Atlantic to significantly alter the Atlantic Meridional Overturning Circulation, but where and how this water leaves the shelf ocean to interact with the boundary currents and deep basins of the subpolar North Atlantic is poorly constrained. This project will use a joint observational and modeling study to explore the pathways and fate of fresh water around Cape Farewell, and to determine the forcing mechanisms that drive the fluxes. Surface drifters and rapidly-profiling Argo floats will be deployed along the southeast Greenland shelf in 2021 and 2022 to assess the along-stream, cross-stream, and vertical coherency of the coastal current. The modeling component will seed a high-resolution (~2 km lateral grid spacing) year-long run of the MITgcm with virtual floats in the coastal current to follow their pathways around Cape Farewell, complemented by an examination of model circulation response to internal instabilities and external forcing, and quantification of the resulting modeled shelf-basin exchange. This work will provide the first comprehensive study of the shelf-basin exchange around Cape Farewell, a process often invoked to explain North Atlantic variability.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.