Contrasting Development and Decay Processes of Indian Ocean Dipoles in the 2000s

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We investigated ocean mixed layer temperature (MLT) balance using moored buoy data together with satellite and atmospheric reanalysis datasets in the eastern Indian Ocean for 2002-2012, a period during which six positive and two negative Indian Ocean Dipole (IOD) events were observed. We focused on the location 5°S, 95°E where in situ measurements of more than 10 years by a TRITON buoy were available. Heat balance analysis demonstrated that horizontal heat advection mainly produced MLT anomalies and that air-sea heat fluxes had a damping effect during the development phase of IOD events. In contrast, during the decay phase, air-sea heat fluxes had a primary role in suppressing MLT anomalies, causing decay of the anomalous IOD conditions. The contributions of horizontal heat advections differed in events, which may be attributed to diversity of IOD evolutions. These results suggest that IOD involves variety of feedback processes during the development and decay phases.