Southern Indian Ocean Dipole as a trigger for Central Pacific El Nino since the 2000s

Abstract

Predicting the El Nino-Southern Oscillation (ENSO) since the 2000s has become increasingly challenging. Here the authors show that the Southern Indian Ocean Dipole has become a key precursor of Central Pacific El Nino since the 2000s with a 14-month lead. Despite decades of effort, predicting the El Nino-Southern Oscillation (ENSO) since the 2000s has become increasingly challenging. This is due to the weaker coupling between the ENSO and well-known precursors in tropical ocean basins, particularly in the Indian Ocean. Here we show that the Southern Indian Ocean Dipole (SIOD), which is characterized by an east-west-oriented sea surface temperature dipole pattern over the southern Indian Ocean, has become a key precursor of Central Pacific El Nino since the 2000s with a 14-month lead. The role of the SIOD in the subsequent year's ENSO is distinctive from the equatorial Indian Ocean Dipole mode in that it prolongs the ENSO period. The westward-shifted ENSO has sustained simultaneous SIOD events for longer periods since the 2000s, which leads to weak but persistent westerly anomalies over the western Pacific. This eventually results in the development of the Central Pacific El Nino in the subsequent year.