Linking the Subsurface Indian Ocean Dipole to Central Pacific ENSO

Abstract

We identified a remote linkage from the Central Pacific (CP) El Niño–Southern Oscillation (ENSO) to the subsurface Indian Ocean dipole (Sub-IOD) occurring in winter-to-spring. Although most Sub-IOD events co-occur with a surface Indian Ocean dipole (IOD) in autumn, some Sub-IOD events develop independently in winter-to-spring. These spring Sub-IODs are usually accompanied by a CP ENSO event that develops in the winter, peaks in early spring, and has a more westward-located sea surface temperature anomaly over the central equatorial Pacific (around 180°E). The sea surface temperature anomaly and the accompanying surface zonal wind anomalie during these western CP El Niño (La Niña) events contributes to an anomalous descending (ascending) branch of the Walker circulation over the Indo-Pacific region and easterly (westerly) anomalies over the equatorial Indian Ocean from winter to the following spring. This helps to trigger a positive (negative) Sub-IOD event.