Distinct Surface Warming Response Over the Western and Eastern Equatorial Pacific to Radiative Forcing

Abstract

This study examines regional characteristics of atmospheric and oceanic feedback processes in the western and eastern equatorial Pacific, by applying a localized surface heating in the respective region in a hierarchy of climate models. A western Pacific forcing is largely offset by a negative shortwave cloud radiative effect and damping via wind-evaporation-SST feedback. In contrast, an eastern Pacific forcing, while being partially compensated for by ocean dynamical adjustments, induces an amplified warming extending to the central Pacific due to weak local damping mechanisms. As for the inter-model spread of the future tropical Pacific surface warming pattern, the ocean heat uptake response in the east can explain much of the spread both on fast (<5 years) and slow (>100 years) timescales. Our results suggest that an “El Niño-like” warming pattern is probable in response to increasing greenhouse gases owing to the strong negative feedback intrinsic to the western Pacific.