Vincent Combes (Oregon State University, United States); Ted Strub (Oregon State University, United States); Corinne James (Oregon State University, United states)

We use the model and altimeter data to characterize the circulation and shelf/deep-ocean interactions over the Agulhas Bank and the Southern Benguela Upwelling Region. The dynamical mechanisms controlling the shelf circulation as well as the shelf/deep-ocean interactions are identified with a suite of process-oriented experiments. Local winds and the sporadic transit of Natal Pulses, which are meanders generated by the transit of Agulhas eddies, are the main drivers of the shelf circulation and shelf/open ocean exchanges. Local winds control the inner shelf circulation and Agulhas eddies the outer shelf. Model analysis reveals a quite energetic water mass exchange between the Agulhas Current and the Agulhas Bank as well as between the Agulhas Bank and the Southern Benguela Upwelling region. We present evidence that shelf/open ocean interactions not only play a fundamental role on the shelf circulation but also on the water mass structure of the open ocean because these interaction lead to an enhanced vertical mixing of Agulhas Current waters. We estimate that the water mass exchanges associated with shelf/open-ocean interactions along the Agulhas Bank are of the same order of magnitude than the Indian/Atlantic interocean exchange.