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

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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.