Victoria mode drives the strengthening of tropical Atlantic SST influence on El Niño-Southern oscillation since the mid-20th century

Abstract Spring tropical North Atlantic (TNA) sea surface temperature (SST) anomalies serve as an important precursor of El Niño–Southern Oscillation (ENSO) development in the following winter. The influence of TNA SST on ENSO has strengthened significantly since the mid-20th century, yet the underlying mechanism remains unclear. Using large-ensemble simulations, AGCM experiments, and the Peter–Clark Momentary Conditional Independence algorithm, we demonstrate that the North Pacific Victoria Mode (VM) is the key modulator of the recent enhancement of TNA SST influence on ENSO. Since the mid-20th century, the North Pacific climate state has shifted toward the negative VM phase, strengthening northeasterly trade winds and enhancing wind–evaporation–SST feedback over the subtropical northeastern Pacific. This background change amplifies the subtropical Pacific SST response to TNA-induced atmospheric anomalies, facilitating their subsequent extension into the tropical Pacific through wind–evaporation–SST feedback and ultimately modulate ENSO development via tropical air–sea interaction. Our results reveal that decadal variation in the North Pacific climate system substantially modulates the tropical Atlantic–ENSO teleconnection.