Mode shift in the Indian Ocean climate under global warming stress

A 115‐year coral record from Kenya has been found to preserve the history of rainfall anomalies in East Africa in relation to global warming‐induced Indian Ocean Dipole (IOD) variability. The coral IOD index demonstrates a dominantly decadal periodicity in the early part of the 20th century. This low‐frequency IOD occurred more frequently before 1924 with mostly quasi‐biennial ranging from 18 months to 3 years events since 1960. The mode shift has also coincided with an intensified coupling with Indian summer monsoon rainfall. We suggest that a warming of the western Indian Ocean, which has attenuated and replaced the El Niño/Southern Oscillation effect over the Indian Ocean, has driven the observed shift.