Boundary-interior exchanges controlling the labrador sea dynamics

The Atlantic Meridional Overturning Circulation (AMOC) quantifies the strength of the northward surface transports and southward deeper transports in the Atlantic Ocean. In particular, as warm surface waters flow northward in the Atlantic they gradually cool on they journey releasing heat to the atmosphere. Then, in the subpolar and polar regions these surface waters become dense enough to sink forming cold deep waters, which return southward through the Atlantic Ocean. This oceanic circulation pattern is of high importance for the Earth’s climate since it is the main distributor of heat, biogeochemical tracers and water masses globally. For decades, both the ocean and climate communities have focused on understanding the dynamics that shape the AMOC strength and most importantly its variability. Although, a lot of progress has been made towards this goal, it is still unclear how the AMOC will respond in a changing climate. Observational and numerical modelling studies are focusing on regions within the Atlantic Ocean that are known to play an important role in shaping theAMOC dynamics. Marginal seas are considered to be such key regions. There the deep waters are formed and then are transported to the global ocean. Although deep water formation regions are located in the interior of the marginal seas it is known that they are not associated with net vertical motions. Instead, several studies suggest that the net downwelling occurs along the perimeter of the marginal seas and that the ocean eddies play an important role in regulating this process. The Labrador Sea, which is located between the west coast of Greenland and the Labrador Peninsula, is known to be one of these key regions in the subpolar North Atlantic. It is characterized by a rich activity of different scale vortices (eddies) that act as a bridge between the boundary current system that encircles the basin and its interior. Therefore, a daunting challenge in physical oceanography is to understand how the ocean eddies interact with the large-scale circulation that sets the strength of the AMOC. This thesis aims to provide a better understanding of the role of the interactions between the boundary current and the interior of the Labrador Sea on its dynamics. It employs a combination of an idealized model, a realistic model and observational data to probe the connection between the key physical processes that shape the Labrador Sea dynamics. Furthermore, it examines to what extent changes in the surface heat fluxes can affect these connections and thus the Labrador Sea dynamics.