Interactive feedback between ENSO and the Indian Ocean in an interactive ensemble coupled model

An interactive feedback between ENSO and the Indian Ocean is investigated using a Center for Ocean Land-Atmosphere Studies (COLA) interactive ensemble coupled model. From a long-term simulation of the coupled GCM, it is shown that El Nino events terminate relatively rapidly when the Indian Ocean SST is anomalously warm. The anomalous Indian Ocean warming induces the anomalous easterlies over the western Pacific by modulating the Walker circulation. In turn, the anomalous easterlies generate oceanic-upwelling Kelvin waves over the western Pacific, which propagate eastward and accelerate the decay of the warm SST in the eastern Pacific. As a result, El Nino terminates relatively quickly, and the phase transition from El Nino to La Nina progresses rapidly. These interactive processes are consistent with those derived from the previous observational analyses.