Revisiting linkages between large-scale and regional ocean processes: Slope Sea variability in the Northwest Atlantic and connections to recent observed trends

The continental shelf and slope system in the Northwest Atlantic has experienced significant changes in recent years. The research work will be driven by the hypothesis that ocean processes within the Slope Sea are the key to understanding interannual to decadal hydrographic variability on the Northeast U.S. continental shelf and slope system. The plan is to synthesize in-situ observations and output from a global high-resolution ocean general circulation model to investigate potential dynamic and hydrographic Slope Sea states, including the Slope Gyre and the Northern Recirculation Gyre, and how they impact the hydrographic properties in the region. Multiple model cycles will allow the assessment of the region’s response to varying strength of the Atlantic Meridional Overturning Circulation (AMOC). The data generated through the proposed work will be of wide use to the oceanographic research community. This project will support two early career researchers as well as undergraduate summer guest students. Results from this project will be incorporated in existing outreach efforts with the Commercial Fisheries Research Foundation in RI and the Cape Cod Commercial Fishermen’s Alliance. The Slope Sea is an important link between regional and large-scale ocean processes, including the AMOC, and has experienced substantial changes in the recent decade. These changes can have important consequences for shelf/open-ocean water exchange and strongly affect shelf dynamics, ecosystems, and stakeholders, such as fisheries. Regional dynamics in the Slope Sea, associated with the recirculation gyres and their interactions with the deep western boundary current and the Gulf Stream have not been addressed in the recent literature, which typically focused on either upstream processes around the Tail of Grand Banks or the Gulf Stream itself. Moreover, observations are too short and sparse to quantitatively investigate decadal scale variability. Realistic high-resolution ocean model simulations will put existing observations and recent trends into longer-term and large-scale context, including SST trends, changes in Slope Currents, and Gulf Stream stability and study associated variability in circulation pathways within the Slope Sea. Furthermore, the simulations can provide novel insights into the regional ocean changes in the Northwest Atlantic resulting from varying strengths of the AMOC, which is difficult to assess from climate models that have too low of a horizontal resolution to resolve the region’s complex circulation. 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.