A decadally delayed response of the tropical Pacific to Atlantic multidecadal variability

Abstract

North Atlantic sea surface temperature anomalies are known to affect tropical Pacific climate variability and El Niño-Southern Oscillation (ENSO) through thermocline adjustment in the equatorial Pacific Ocean. Here coupled climate simulations featuring repeated idealized cycles of the Atlantic Multidecadal Oscillation (AMO) generated by nudging its tropical branch demonstrate that the tropical Pacific response to the AMO also entails a substantial decadally delayed component. The simulations robustly show multidecadal fluctuations in central equatorial Pacific sea surface temperatures lagging the AMO by about three decades and a subdecadal cold-to-warm transition of the tropical Pacific mean state during the AMO's cooling phase. The interplay between out-of-phase responses of seawater temperature and salinity in the western Pacific and associated density anomalies in local thermocline waters emerge as crucial factors of remotely driven multidecadal variations of the equatorial Pacific climate. The delayed AMO influences on tropical Pacific dynamics could help understanding past and future ENSO variability.