Mixing and Energy Flux Estimates from Hydrographic Measurements in the Deep Western Boundary Current of the North Atlantic

Abstract

Diapycnal diffusivity and energy dissipation along the western boundary of the North Atlantic have been inferred from more than 100 profiles of combined LADCP and CTD measurements collected at four different latitudes in the North Atlantic. Both diffusivity and dissipation were elevated at all four sites. Repeated measurements in the Deep Western Boundary Current (DWBC) at 47N and at 16N yield a velocity dependent energy dissipation rate for high core velocities, and a velocity independent background. Combined with the vertical energy flux direction and the lack of tidal signals the velocity dependence indicates that interaction between mean flow and bottom topography is the dominant process for the elevated mixing. Semi-diurnal energy fluxes in horizontal direction have been estimated from repeated measurements at 16N, 47N, and 49N. Integrated energy flux at 47N and 49N is directed along the shelf, while it is in uphill direction at 16N.