Observational analysis suggests that the western tropical Pacific (WTP) sea surface temperature (SST) shows predominant variability over multidecadal time scales, which is unlikely to be explained by the Interdecadal Pacific Oscillation. Here we show that this variability is largely explained by the remote Atlantic multidecadal oscillation (AMO). A suite of Atlantic Pacemaker experiments successfully reproduces the WTP multidecadal variability and the AMO–WTP SST connection. The AMO warm SST anomaly generates an atmospheric teleconnection to the North Pacific, which weakens the Aleutian low and subtropical North Pacific westerlies. The wind changes induce a subtropical North Pacific SST warming through wind–evaporation–SST effect, and in response to this warming, the surface winds converge towards the subtropical North Pacific from the tropics, leading to anomalous cyclonic circulation and low pressure over the WTP region. The warm SST anomaly further develops due to the SST–sea level pressure–cloud–longwave radiation positive feedback. Our findings suggest that the Atlantic Ocean acts as a key pacemaker for the western Pacific decadal climate variability.

The Victoria mode (VM) represents the second dominant mode (empirical orthogonal function, EOF2) of North Pacific variability, independent of the Pacific Decadal Oscillation and is defined as the EOF2 of SST anomalies in the North Pacific poleward of 20°N. The present study indicates that the VM is closely linked to the development of El Niño-Southern Oscillation (ENSO). The VM may effectively act as an ocean bridge (or conduit) through which the extratropical atmospheric variability in the North Pacific influences ENSO. The VM can trigger the onset of ENSO via the following two dominant processes:(1) surface air-sea coupling associated with the VM in the subtropical/tropical Pacific and (2) evolution of subsurface ocean temperature anomalies along the equator associated with the VM. These two processes may force sufficient surface warming to occur in the central eastern equatorial Pacific from spring to summer, which in turn initiates an ENSO event. The VM influence on ENSO relies on a basin-scale air-sea interaction dynamic, as opposed to more local-scale dynamics typically associated with the seasonal footprinting mechanism or Pacific meridional mode. The majority of VM events are followed by ENSO events. These ENSO events triggered by VM include El Niño Modoki (EM) as well as conventional El Niño. There is no evidence that the VM tends to be more conducive to the initialization of EM than conventional El Niño.

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