ENSO modulation of the upwelling season off southern-central Chile

Southern-central Chile (35 degrees-41 degrees S) is characterized by strong seasonality of coastal upwelling. At these latitudes, El Nino-Southern Oscillation (ENSO) forces climatic changes mainly through atmospheric teleconnections. Here we show that ENSO also modulates the timing, i.e. onset and end, of the upwelling season. In order to study the ENSO related wind-driven upwelling changes, compositing analysis was applied to coastal winds and to other atmospheric fields. During El Nino (La Nina) austral spring conditions, delayed (earlier-normal) onset of the upwelling season is associated with a meridional dipole characterized by weaken (stronger) South Pacific subtropical anticyclone and blocking (cyclonic) systems in the Amundsen-Bellingshausen Seas. During austral fall season, similar meridional dipole pattern described for spring La Nina conditions is related to delayed end of the upwelling season. Accordingly, shorter (longer) duration and weaker (stronger) intensity of upwelling season occurs during El Nino (La Nina) events off southern-central Chile. Citation: Montecinos, A., and F. Gomez (2010), ENSO modulation of the upwelling season off southern-central Chile, Geophys. Res. Lett., 37, L02708, doi:10.1029/2009GL041739.