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

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.