Equatorially forced intraseasonal propagations along the Peru-Chile coast and their relation with the nearshore eddy activity in 1992-2000: A modeling study

A regional eddy-resolving oceanic model spanning the 1992-2000 period is used to study the influence of 50 to 80 day intraseasonal equatorial Kelvin waves (IEKW) on mesoscale eddy activity off the west coast of Peru and northern and central Chile. The model is shown to realistically simulate nearshore intraseasonal sea level variability, poleward propagation of equatorially forced coastal trapped waves along the coastal waveguide, and offshore variability related to mesoscale eddies and Rossby waves (RW). In agreement with linear theory, RW are confined equatorward of similar to 12 degrees S in the 50-80 days period range. South of that critical latitude, westward propagation is dominated by energetic mesoscale signals resulting mainly from coastal flow instability. Sensitivity experiments to the open boundary conditions are then used to estimate to what extent eddy activity is impacted by the remote equatorial forcing. A coastal increase in eddy kinetic energy related to the energetic 60 day IEKW activity present in the open boundary forcing is evidenced and is largest off northern Peru, whereas no major changes are observed offshore. Additional regional simulations with different open boundary conditions corroborate our findings and suggest that this limited effect of IEKW on the offshore eddy kinetic energy may be a robust feature.