Role of the Spring Sea Surface Temperature over Southeastern Indian Ocean in Bridging the Indian Ocean Dipole and Subsequent ENSO

Abstract A significant relationship exists between the Indian Ocean Dipole (IOD) and the following year’s El Niño-Southern Oscillation (ENSO), in spite of the uncertainty in the associated mechanisms. Here we show that the spring sea surface temperature (SST) anomalies over the southeastern Indian Ocean (SEIO) play a bridging role in the teleconnection of the IOD and subsequent year’s ENSO. A positive IOD could induce a positive tendency of SST in the SEIO region from autumn to winter, primarily through the cloud-radiation-SST feedback, forming an anomalous SEIO warming which persists into the subsequent spring. As the oceanic forcing dominates in spring, the SEIO warming can induce/maintain the anomalous anticyclonic circulation over the western North Pacific according to the Gill-model response, accompanied by easterly wind anomalies over the western equatorial Pacific that generate eastward propagating upwelling Kelvin waves. As a result, anomalous cooling appears in the central-eastern tropical Pacific in the following seasons, manifesting as a La Niña mode. Additionally, the role of the ocean channel (i.e. the Indonesian Throughflow) in connecting the spring SEIO SST and the subsequent eastern Pacific SSTs is also discussed.