Modelling the Agulhas current system with FRAM (fine resolution antarctic model)

The FRAM (Fine Resolution Antarctic Model) is a primitive equation numerical model of the ocean south of 24°S. Because of its fine vertical as well as horizontal spatial resolution, its short numerical integration time steps and limited relaxation constraints, it develops a range of currents, fronts and eddies at the mesoscale which appear very realistic. Comparison between the model and known features of the Agulhas Current system is carried out since this particular flow regime has some of the most intense circulatory features in the global ocean. It is shown that FRAM simulates the hydrographic characteristics and kinematic behaviour of a large number of circulation components of the Agulhas system with remarkable success. These include the retroflection of this current, the shedding of rings and their subsequent advection across the South Atlantic, and the formation of eddies across the Subtropical Convergence. Smoothing of the bottom topography in the model may seriously affect western boundary currents that are very sensitive to depth changes.