Diverse impacts of Indian Ocean dipole on El Niño-Southern Oscillation

Understanding the impact of the Indian Ocean dipole (IOD) on El Nino-Southern Oscillation (ENSO) is important for climate prediction. By analyzing observational data and performing Indian and Pacific Ocean pacemaker experiments using a state-of-the-art climate model, we find that a positive IOD (pIOD) can favor both cold and warm sea surface temperature anomalies (SSTA) in the tropical Pacific, in contrast to the previously identified pIOD-El Nino connection. The diverse impacts of the pIOD on ENSO are related to SSTA in the Seychelles-Chagos thermocline ridge (SCTR; 60 degrees-85 degrees E, 7 degrees-15 degrees S) as part of the warm pole of the pIOD. Specifically, a pIOD with SCTR warming can cause warm SSTA in the southeastern Indian Ocean, which induces La Nina-like conditions in the tropical Pacific through interbasin interaction processes associated with a recently identified climate phenomenon dubbed the "warm pool dipole.'' This study identifies a new pIOD-ENSO relationship and examines the associated mechanisms.