Assessment of inter-annual and seasonal variability of the circulation over the shelf and slope off central Chile

Assessment of inter-annual and seasonal variability of the circulation over the shelf and slope off central Chile and the development of simple models of free and wind-forced trapped waves Hydrographic data together with current, sea level and wind time-series from several places along the west coast of South America were used to assess the temporal variability along this region. An important set of current meter data used here were obtained during an international study of the Humboldt Current system, as a contribution to the Joint Global Flux Study Project (JGOFS). The extension of this observational effort, supported in a second phase by the FONDAP-Humboldt programme, have allowed the completion of an 8 year record of moored current and temperature over the slope off Coquimbo, near 30S. A sister mooring, located about 500km south from Coquimbo, near 34 45'S, was maintained during October 1992 and July 1995 in order to study the alongshore propogation of current fluctuations. Time series of wind, sea-level and atmospheric pressure have been analysed and current records used to address the time variability at several scales over the slope off Chile. They encompass the moderate 1991-1992 and the strong 1997-1998 El Nino events and the 1995-96 and 1998 La Nina events. Interannual fluctuations of alongshore currents off 30S and seal level along the west coast of South America were analysed using a linear model forced by observed equatorial signal and regional wind stress. In addition, a wind-forced coastal trapped wave model was implemented and run. The circulation off Peninsula de Mejillones was analysed from hydrographic profiles and current-meters moored during January and July 1997.