Optimal Growth of IPV Lags AMV Modulations by up to a Decade.

The Interdecadal Pacific Variability (IPV) has global climate effects but its decadal prediction is a challenge. Here, we use linear inverse models to study the optimal growth of the IPV and reveal important precursor patterns. We find that the optimal growth of the IPV exists in observations due to interference among various sea surface temperature (SST) decadal variations. Small SST anomalies extending from the northeastern subtropical Pacific to the central tropical Pacific, in concert with thermocline dynamics, can develop into a mature phase of the IPV after ∼3 years. Furthermore, the initial SST anomalies lag the Atlantic Multidecadal Variability (AMV) by up to a decade, suggesting the potential importance of the AMV in IPV decadal predictability. As climate models commonly underestimate the AMV trans‐basin effect, our study calls for more efforts on reducing the model bias to improve IPV decadal prediction. Plain Language Summary: The Interdecadal Pacific Variability (IPV), the leading decadal mode in the Pacific Ocean, can modulate global climate system with broad ecological and socioeconomic influences. However, as partly the residual of El Niño‐Southern Oscillation that shows predictability lower than 2 years, the IPV may be hard to be predicted several years ahead. Here, by using a method called optimal growth, we reveal that an ∼3‐year growth of IPV variance is associated with northeastern subtropical Pacific SST variability and ocean dynamics. Specifically, the Atlantic Multidecadal Variability (AMV), a main climate mode in the Atlantic Ocean, can provide potential decadal predictability to the optimal growth of the IPV. This trans‐basin effect is, however, underestimated in general circulation models that are commonly used for climate prediction. Hence, our study implies that reducing the model bias of the AMV trans‐basin effect will lead to more reliable IPV decadal prediction. Key Points: The Interdecadal Pacific Variability (IPV) exhibits ∼3‐year optimal growth, a time length beyond the upper bound of El Niño‐Southern Oscillation predictabilityThe optimal growth of the IPV is associated with northeastern subtropical sea surface temperature variability and pan‐tropical Pacific thermocline dynamicsThe Atlantic Multidecadal Variability leads the optimal growth of the IPV by up to a decade, an important factor for IPV decadal prediction [ABSTRACT FROM AUTHOR]