Impact of a coastal-trapped wave on the near-coastal circulation of the Peru upwelling system from glider data

Geostrophic alongshore velocity data from a glider repetitive section off the coast of Peru (14°S) are used to study the cross-shore structure and temporal variability of the Peru current system during a 5 week period in April-May 2010. Besides providing substantial information on the surface frontal jet associated with the Peru Coastal Current and the surfacing Peru-Chile Undercurrent that flows poleward trapped on the continental shelf and slope, the glider data reveal the presence of an intense deep equatorward current, which transports up to ∼2.5 Sv. The dynamics of this current are investigated using an eddy-resolving regional model. The variability of the vertically sheared alongshore flow is shown to be related to the passage of a poleward propagating coastal-trapped wave likely of equatorial origin. Solutions from a two-dimensional, linear, coastal wave model suggest that the alongshore current observed vertical structure is associated with the second and third baroclinic modes of the coastal-trapped wave.