The Varying Equatorial Pacific-Equatorial Atlantic Teleconnection

SST variations in the eastern equatorial Pacific can influence the equatorial Atlantic SST not only through the atmospheric response that propagates east to the equatorial Atlantic but also through the dynamic ocean-atmosphere interaction (Bierknes feedback) in the equatorial Atlantic that works against the atmospheric response. These two processes probably exist in all the seasons but their relative strength may vary as season progresses or the mean state changes. When the mean state of eastern tropical Pacific SST is warmer (colder) than normal, the induced anomalous atmospheric circulation causes the mean thermocline in eastern equatorial Atlantic shallower (deeper), enhancing (weakening) the Bjerknes feedback. During the Pacific warm period, when eastern Pacific SST is warmer (colder) than normal on interannual time scale, the net response in equatorial Atlantic SST is a cold (warm) anomaly because of the enhanced Bjerknes feedback, thus the correlation between Nino-3 index and Atlantic-3 index is negative. While during the Pacific cold period, the correlation between the indices is positive due to weakened Bjerknes feedback.