Poleward propagating perturbations in currents and sea levels along the Peru Coast

Abstract

In 1976 and 1977 current measurements were made on the Peru continental shelf and slope as part of the Coastal Upwelling Ecosystems Analysis expedition Joint II. The fluctuations in current were not well correlated with the local wind, in contrast to observations from coastal upwelling regions off Oregon and northwest Africa. Data from current meter arrays at separations up to 700 km are available for periods of 40–75 days. Subtidal (0.05–0.25 cpd) fluctuations propagate coherently at 200 km d−1 in a poleward direction. Analysis of current, water temperature, and sea level time series suggests that these fluctuations have an offshore scale of 70 km and represent baroclinic Kelvin waves, whose origin is equatorward of 10°S and which propagate to at least 15°S.