Atlantic Impacts on Subdecadal Warming over the Tropical Pacific in the 2000s

Abstract:

A subdecadal (i.e., 3-year-running means) variation over the tropical Pacific is very distinctively observed in the 2000s. Here, we have demonstrated that sea surface temperature (SST) anomalies in the tropical Atlantic contribute to forming high ocean temperature anomalies of the tropical Pacific in the early-2000s, by performing partial data assimilation of global climate model. Low SST over the equatorial Atlantic changes the Walker circulation and the associated weakening of the Pacific trade wind raises the equatorial SST on the subdecadal timescales. At the same time, high SST anomaly is generated also in the off-equatorial North Pacific through deepening of the upper ocean thermocline due to an accompanying anti-cyclonic surface wind anomaly aloft. While the north tropical Atlantic SST may help the subdecadal warming in the equatorial Pacific, the resultant SST anomalies show 1-year delay in phase transition and are modestly accompanied by the ocean thermocline deepening.