Observed of Equatorial Currents in the Indian Ocean during Two Contrasting IOD Events: 2006 and 2010

Abstract

The evolution of Indian Ocean Dipole (IOD) events in 2006 and 2010 is investigated using observational data products that are made to understand several processes in the positive (negative) phase of IOD events. Two Acoustic Doppler Current Profiler (ADCP) moorings mounted at 90°E and 80.5°E along the equator were used to evaluate the zonal current variation during two contrasting Indian Ocean Dipole (IO) events. Westward anomalies of the zonal current were observed at 0°, 80.5°E during the peak phase of the positive IOD event from October to December 2006. Meanwhile, the observed zonal currents at 0°, 90°E only showed the short-term westward anomalies during October 2006. On the other hand, during the negative IOD event in 2010, the observed zonal current at both mooring locations indicated strong intraseasonal variations of the eastward anomalies from August to December 2010. Strong easterly (westerly) anomalies of the surface zonal winds were observed during the peak phase of the positive (negative) IOD event in 2006 (2010). These easterly (westerly) anomalies forced upwelling (downwelling) equatorial Kelvin waves indicated by the negative (positive) sea surface height anomalies. Strengthening (weakening) of upwelling (downwelling) along the equatorial Indian Ocean would be a significant factor for further understanding of IOD evolution.