A major El Niño event is developing in the Equatorial Pacific Ocean. The current oceanic state in the Equatorial Pacific is compared with previous El Niño events to gain a potential sense about future development and related impacts. Changes in sea level can be used as an indicator of the changes in the heat content, and changes in sea surface temperature (SST) are indicative of the coupling between the ocean and the atmosphere from wind forcing.
The animation shows differences between SST anomalies during the 1997-1998 El Niño and 2015-2016 events. Large positive anomalies are observed off the West Coast of North America throughout 2015 and large positive SST anomalies as early as May 2015 in the Equatorial Pacific in comparison with the 1997-1998 El Niño events. Comparison of sea level anomalies (not shown) also indicate significant differences between the two events. In January 1997, sea level anomalies in the Tropical Pacific were still close to normal, while in 2015 large anomalies have already appeared. It is clear from these comparisons that not all El Niños are alike. The events show differences in both the spatial patterns of peak warming and also the time of year when the maximum anomalies occur.