Dynamics of separating western boundary currents in ocean models

Western boundary current (WBC) separation dynamics are investigated in a two-layer quasigeostrophic model of a wind-driven subtropical ocean gyre. The results suggest that the vorticity in the thin cyclonic layer next to the coast plays a key role in the WBC separation mechanism. It is found that the outflow from the western boundary current is a region where this cyclonic vorticity diminishes rapidly downstream, through the combined action of Laplacian viscosity and eddy vorticity flux divergence. These results are consistent with earlier work on laminar, unstratified WBC dynamics, and extend those findings to the more realistic case of turbulent, stratified flow.