24th Pacific Science Congress (PSC-24)

As prominent modes of decadal climate variability, the Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Variability (AMV) exert significant influences on the global climate system. Numerous model studies indicate rapid interaction between the IPO and AMV via atmospheric teleconnections. In contrast, however, observational data reveal only a weak contemporaneous IPO-AMV correlation, presenting a critical challenge. To resolve this discrepancy, we apply a linear inverse model (LIM) to observational data. Our analysis demonstrates that a mutual cancellation effect inherent in their bidirectional interaction suppresses the observed contemporaneous correlation. However, when the LIM is constrained to isolate only one-way forcing (either IPO forcing AMV or AMV forcing IPO), the correlation peaks near-simultaneously. This one-way forcing observational LIM robustly aligns with model pacemaker experiments that support rapid IPO-AMV interaction. Furthermore, we show that this fast interaction is mediated by processes spanning both the tropics and extratropics. This study thus reconciles the inconsistency between models and observations regarding IPO-AMV interaction, with important implications for global climate prediction. Furthermore, it highlights that the commonly used correlation analysis in climate science may obscure underlying realistic dynamical linkages in a coupled system.

Interdecadal Pacific Oscillation,Atlantic Multidecadal Variability,Decadal variability,ocean-atmosphere interaction