The Role of Ocean Dynamical Thermostat in Delaying the El Niño–Like Response over the Equatorial Pacific to Climate Warming

AbstractThe role of ocean dynamics in the response of the equatorial Pacific Ocean to climate warming is investigated using both an atmosphere–ocean coupled climate system and its ocean component. Results show that the initial response (fast pattern) to an uniform heating imposed on the ocean is a warming centered to the west of the date line owing to the conventional ocean dynamical thermostat (ODT) mechanism in the eastern equatorial Pacific—a cooling effect arising from the up-gradient upwelling. In time, the warming pattern gradually propagates eastward, becoming more El Nino–like (slow pattern). The transition from the fast to the slow pattern likely results from 1) the gradual warming of the equatorial thermocline temperature, which is associated with the arrival of the relatively warmer extratropical waters advected along the subsurface branch of the subtropical cells (STCs), and 2) the reduction of the STC strength itself. A mixed layer heat budget analysis finds that it is the total ocean dynamic...

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