Ocean Surface Warming Pattern Inhibits El Niño–Induced Atmospheric Teleconnections

Abstract

Abstract The ocean surface temperature has warmed dramatically over most of the globe in recent decades, which shows the west warmed faster than the east (“La Niña–like” warming) in the equatorial Pacific. It differs from the simulated “El Niño–like” warming in existing studies that discussed the El Niño–induced teleconnection response to global warming. Some studies have indicated that El Niño teleconnections are sensitive to the ocean surface warming patterns, but the mechanisms are still elusive. Here, reanalysis data and numerical experiments were analyzed to investigate how winter El Niño atmospheric teleconnections respond to the historical ocean surface warming. We show that the inhibited effect of the El Niño on the North African winter climate through the suppressed Walker circulation over Atlantic–Africa–Indian Ocean sectors under the ocean surface warming matches the observed changes. Also, the model reproduces the observed weakening of the El Niño–induced Pacific–North American wave and its suppressed downstream propagation in the ocean surface warming scenario because of the reduction in contributions of the vortex stretching to the El Niño–induced wave sources in the subtropical jet streams. Our findings demonstrate the important role of ocean surface warming patterns in the projections of the El Niño–induced atmospheric teleconnection.