Modelling the Response of Shelf Waters to Agulhas Current Variability.

The shelf regions inshore of the Agulhas Current are characterized by the strong influence of the highly turbulent and dynamic nature of the western boundary current. Exchange of water onto the shelf appears dominated by shear edge dynamics, from boundary eddies and filaments of warm surface water to the large solitary meanders present in the Agulhas Current. In addition geographically defined upwelling cells are present along the coast, which are hypothesized to maintain an advectively driven thermocline on the inner shelf regions. Due to the uncertainty of model solutions in the Agulhas Current, a multi-model approach is employed using both HYCOM and NEMO simulations at a 10km resolution, as well as higher resolution experiments, to reduce the dependency of the analysis on individual model biases. These multi-model results, in conjunction with mooring and satellite observations, allow for the development of a time series of meander activity. Results show the response of the shelf waters to be sensitive to the nature of the initial meander perturbation, with the main mode of variability occurring at shorter timescales than the large solitary meanders. The role of the widening bathymetry along the shelf on vorticity dynamics and eddy generation on the inshore front of the Current is also explored.