Sensitivity of the Northern Humboldt Current System nearshore modeled circulation to initial and boundary conditions

The influence of the eastern Pacific equatorial circulation on the dynamics of the Northern Humboldt Current System is studied using an eddy-resolving regional circulation model forced by boundary conditions from three distinct ocean general circulation models. The seasonal variability of the modeled nearshore circulation and the mesoscale activity are contrasted in order to evaluate the role of the density forcing. The seasonal variability of the surface and subsurface alongshore currents strongly depends on the amplitude and timing of the seasonal eastward propagating equatorial waves. The equatorward flow and upwelling intensity are also impacted by nonlinear processes, such as the seasonal generation of nearshore mesoscale eddies, which create alongshore pressure gradients modulating the surface current. Boundary conditions affect differently the intensity and phase of the eddy kinetic energy, as baroclinic instability is triggered by coastal waves during austral summer and fall, whereas it is sustained by the wind-driven upwelling during austral winter.