Intensity changes of Indian Ocean dipole mode in a carbon dioxide removal scenario
Soon‐Il An, Hyo-Jin Park, Soong‐Ki Kim, Jongsoo Shin, Sang‐Wook Yeh, Jong‐Seong Kug
Abstract
Abstract The Indian Ocean Dipole/Zonal mode (IOD) is an interannual phenomenon over the tropical Indian Ocean, causing a pronounced impact worldwide. Here, we investigate the mechanism of the change in IOD characteristics in a CO 2 removal simulation for an earth system model (ESM). As the CO 2 concentration increases, the intensity of IOD tends to increase, but at high CO 2 concentrations, further increases decrease the IOD intensity. The minimum IOD amplitude was recorded during the early decrease in CO 2 . First, we developed a conceptual model for IOD that is composed of local air-sea coupled feedback, delayed ocean dynamics, El Niño impact, and noise forcing. Then, by adopting ESM results into this simple IOD model, we revealed that the local air–sea coupled feedback is a major factor for changing IOD amplitude, while El Niño does not exert a change in IOD amplitude. The local air–sea coupled feedback including thermocline feedback, wind-evaporation feedback, and Ekman feedback is strongly modified by the air–sea coupling strength during progression of a global warming. Consequently, under the higher CO 2 concentrations, IOD amplitude is reduced due to the weakening of air-sea coupling over tropical Indian Ocean.