Unraveling the interactions between tropical Indo-Pacific climate modes using a simple model framework

The dominant interannual climate phenomena are mainly observed in the tropical Indo-Pacific Ocean. While climate modes such as the El Niño–Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Indian Ocean Basin (IOB) can develop through intrinsic basin dynamics, interactions between the Pacific Ocean (PO) and Indian Ocean (IO) significantly modulate their characteristics. Here, we quantified the impacts of tropical Indo-Pacific coupling using an extended nonlinear recharge oscillator model for ENSO that incorporates key tropical IO climate modes. Enabling the PO-to-IO effect increased the amplitudes of the IOD and IOB by 23% and 38%, respectively, and regulated IOB seasonality. Conversely, IO-to-PO connection increased ENSO peak variability by 5%, shortened its periodicity by 1 year, and more than doubled the frequency of extreme ENSO events when coupling strength was doubled. Over the past decade, strengthened Indo-Pacific interactions resulting from positive feedback between basins, have contributed to increased variability and occurrence of major climate modes.