Causal Links on Interannual Timescale Between ENSO and the IOD in CMIP5 Future Simulations

Abstract

AbstractHere we investigate the causal links of interannual variability between the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) in Coupled Model Intercomparison Project Phase 5 (CMIP5) RCP8.5 future simulations. The analyses account for possible simultaneous impacts of the southern annular mode and the Indian summer monsoon rainfall on future ENSO‐IOD connection. We found robust causal influence of ENSO on IOD for majority (14/22) of models. ENSO variations cause changes of tropical Indian Ocean zonal wind and sea surface temperature and thus directly influence IOD. However, the specific mechanisms of this impact remain elusive in multimodel point of view. The results show significant impact of IOD on ENSO in the 2006–2100 period for 10/22 models. These results suggest that ENSO influence on IOD is slightly more robust than vice versa. We emphasize the uncertainty in the two‐way future causal relationship between ENSO and IOD.