Indian Ocean dipole response to global warming: Analysis of ocean-atmospheric feedbacks in a coupled model

Low-frequency modulation and change under global warming of the Indian Ocean Dipole (IOD) mode are investigated with a pair of multi-century integrations of a coupled ocean-atmosphere general circulation model, one under constant climate forcing and one forced by increasing greenhouse gas concentrations. In the unforced simulation, there is significant decadal and multidecadal modulation of the IOD variance. The mean thermocline depth in the eastern equatorial Indian Ocean (EEIO) is important for the slow modulation, skewness and ENSO-correlation of the IOD. With a shoaling (deepening) of the EEIO thermocline the thermocline feedback strengthens, this leads to an increase in IOD variance a reduction of the negative skewness of the IOD and a weakening of the IOD-ENSO correlation. In response to increasing greenhouse gases, a weakening of the Walker circulation slows leads to easterly wind anomalies in the equatorial Indian Ocean; the oceanic response to weakened circulation is a thermocline shoaling in the EEIO. Under greenhouse forcing, the thermocline feedback intensifies but surprisingly IOD variance does not. The zonal wind anomalies associated with IOD are found to weaken, likely due