A coupled model study of glacial Asian monsoon variability and Indian Ocean dipole

Abstract

A coupled climate model is used to study the response of interannual variability of Asian summer monsoon, and its relation with tropical climate variability over the Pacific and Indian Oceans. Two simulations are performed, one for the present and the other for the Last Glacial Maximum. It is found that at glacial times, the weakened Asian monsoon climatology results in a significant shallowing of mean tropical thermocline in the central-western Indian Ocean. This shallower thermocline intensifies the positive ocean-atmosphere feedback in the western Indian Ocean, and therefore contributes to an enhanced Indian Ocean Dipole (IOP) variability. The increased IOD variability in turn exerts a stronger affect on the variability of South Asian monsoon rainfall, and therefore may have contributed to a significant reduction of correlation between the monsoon and the Pacific El Niño/Southern Oscillation (ENSO) variability. © 2007, Meteorological Society of Japan.