Coastal Retention and Mesoscale Dispersion Processes in Upwelling Systems

Patrick Marchesiello
IRD, Centre de Bretagne, France

The structure and dynamical mechanisms of coastal upwelling and associated mesoscale physical variability in the major upwelling systems is addressed using the Regional Oceanic Modeling System. Coastal upwelling is associated to a narrow coastal divergence forced by alongshore winds and localized offshore of a frictional innershelf zone which can provide in some cases a precious retention area for marine organisms. On the offshore side of the upwelling front, the primary eddy generation mechanism is the baroclinic instability of upwelling, alongshore currents, with important influences by capes and ridges in launching transient filaments and fronts. This mesoscale activity is associated with intense cross-shore exchanges of water and material properties resulting in offshore dispersion of coastal properties.

We are presenting a modeling strategy to study both retention and dispersion processes on the continental shelf and within the coastal transition zone of upwelling regions. We will show for example that the physical parameters defining the California and Canary current systems may lead to fundamental differences with respect to these processes.