The subtropical northeastern Pacific (SNEP) acts as a bridge conveying information between the North and tropical Pacific. While most studies have investigated the SNEP sea surface temperature (SST) interannual variability, less attention has been paid to the pronounced decadal variability in this region. Here, by analyzing observational data and an ensemble pacemaker simulation, we investigate SNEP SST decadal variability in terms of atmospheric forcing processes. We find that both tropical Pacific-forced and internal (independent of tropical Pacific forcing) atmospheric variability play important forcing roles. In particular, tropical Pacific-excited Aleutian low variability, whose center of action shifts southeastward compared to the climatology, contributes to forcing SNEP SST decadal variability. This contribtution could offer an important source for the predictability of SNEP SST decadal variability.

Equatorial Pacific decadal variability (EPDV) modulates global climate. Although EPDV is suggested to be generated by both air-sea thermodynamically coupled slab ocean models (SOM) and fully coupled dynamic ocean models (DOM), the reason of EPDV simulated by the two distinct hierarchies of models remains unclear. This ambiguity arises from a gap in the dynamical framework between SOM and DOM. To fill the gap, we conducted a novel experiment (Clim-tau) that retains only the effects of thermodynamic coupling and mean ocean current on EPDV (without anomalous ocean current). We showed that in Clim-tau, thermodynamic-driven EPDV as in SOM is largely damped by equatorial Pacific mean upwelling; whereas involving anomalous ocean current as in DOM, the damped EPDV will be further amplified. Finally, we discussed the role of ocean dynamics in the observed EPDV. Our study highlights that SOM may misinterpret the physical mechanisms in the regions where ocean dynamics is important.