Recent Changes of Pacific Decadal Variability Shaped by Greenhouse Forcing and Internal Variability

Abstract

Pacific Decadal Variability (PDV) has enormous influences on North American and Eurasian climate and Pacific ecosystems. Its change under anthropogenic warming is of prodigious societal concern and scientific dispute. We show evidence that the observed PDV has amplified in the northeast Pacific horseshoe-like region while weakened over the South Pacific and Kuroshio-Oyashio Extension (KOE) region since the beginning of the 21st century. Congruently, under the influence of PDV, precipitation anomalies have significantly amplified globally and reversed the sign over Africa and East Asia. Analysis of the Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations and future projections suggests that greenhouse forcing weakens the PDV in the South and northwestern Pacific and shortens its periodicity. However, the observed PDV's enhancement over the North Pacific eastern boundary is likely due to internal variability. Our findings on the PDV's response to anthropogenic forcing and internal variability shed light on the PDV's future change and decadal prediction.