Dynamics of North Atlantic Western Boundary Currents

Isabela Le Bras, Ph.D., 2017
John Toole, Advisor

This thesis employs a combination of theory, observations and models to probe the dynamics of the Gulf Stream and Deep Western Boundary Current (DWBC).

First, a depth-averaged vorticity budget framework is developed and applied to observations and state estimate data in the Gulf Stream region. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component.

The next chapter focuses on the propagation of water mass anomalies in the DWBC. Measurements of the DWBC at Line W reveal water mass changes that are consistent with changes in the Labrador Sea and along the path of the DWBC. Using a simple model, we diagnose a first order role for both advection and stirring in the DWBC.

The final study brings the currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can merge with the DWBC at depth, and eddy fluxes associated with its adjustment stir the DWBC with the interior.