Role of non-linear oceanic processes in the response to westerly wind events: New implications for the 1997 El Niño onset

Abstract

In March 1997, a strong westerly wind event (WWE) occurred in the western equatorial Pacific prior to the 1997-1998 El Niño event. It produced downwelling Kelvin waves that interacted non linearly with the surface temperature, salinity and zonal current fronts located at the eastern edge of the warm-fresh pool (EEWP). This non-linear interaction locally increased zonal currents by a factor of three compared to a theoretical linear response, and advected the EEWP at an unexpected rate (~ 1m/s) to which the ocean-atmosphere coupled system may have been responding rapidly to trigger El Nino conditions.