Contrasting Interbasin Climate Influences Driven by Externally Forced SST Changes in the Tropical Ocean Basins

A suite of pacemaker experiments is conducted to study interbasin climate influences driven by externally forced sea surface temperature (SST) changes in each of the three tropical oceans. The pattern of SST changes in the tropical ocean basins are based on experiments with the community Earth System Model whereby the CO₂ concentration is instantaneously quadrupled relative to preindustrial levels, as well as the ensemble difference between the historical and IpctCO₂ runs of 20 models participating in CMIP5. In the CESM, the most significant interbasin teleconnection emanates from the tropical Atlantic Ocean. Warming associated with the Atlantic multidecadal oscillation leads to an atmospheric teleconnection to the North Pacific, inducing a subtropical meridional SST pattern through the westward displacement of the Pacific Walker circulation and a cooling of the tropical Pacific. The pattern of SST changes in the CMIP5 ensemble is fairly different, leading to considerable differences in the interbasin teleconnection patterns in comparison to the CESM; attesting to the sensitivity of the coupled system to changes in the pattern of SST under external radiative forcing and inter-model biases.