Models of the diffusive–advective balance at the subtropical convergence

Abstract

Horizontal and vertical diffusion coefficients are calculated by fitting different types of diffusive-advective models to the scales of a specified anomaly in the salinity field near the Subtropical Convergence. Comparison of the calculated coefficients with those in the literature reveal the balance in the mixed layer near the convergence is between horizontal diffusion and northward advection. Below the mixed layer at the convergence the balance is between southwards and upward advection and mainly horizontal diffusion. A tongue of saline water extends south from the convergence with its core at a depth of about 100 m. The balance in this tongue is consistent with a uniform slow northwards flow with parabolic shear and horizontal and vertical diffusion.