A multi-centennial tree-ring δ¹⁸O record reveals a late-1970s wetting shift in the Changbai Mountains, Northeast China: Linkages to a transition to the negative PDO phase

In a warming climate, intensified air–sea evaporation and circulation adjustments are reshaping precipitation patterns and may alter the occurrence of hydroclimatic extremes. The Changbai Mountains, situated at the interface between the monsoon and the westerlies, form a critical corridor for moisture transport and rainfall formation in Northeast China, yet the dominant circulation controls on regional precipitation variability remain debated. Here we develop an annually resolved tree-ring δ¹⁸O series from endemic Changbai pine (Pinus sylvestris L. var. sylvestriformis) and identify a pronounced climatic “memory effect” in tree-ring δ¹⁸O fractionation, with February–August precipitation emerging as the dominant control (R² > 0.4), enabling reconstruction of precipitation variability in the study area over the past 235 years. The reconstruction exhibits pronounced interannual-to-interdecadal variability and a stepwise wetting–drying–rewetting trajectory, with major turning points in the late 1830s and late 1970s, and identifies three extremely wet years and four extremely dry years. Wavelet transform coherence (WTC) and cross-wavelet transform (XWT) analyses reveal significant time–frequency coherence between the Pacific Decadal Oscillation (PDO) and the reconstructed interannual precipitation series across multiple bands; interdecadal comparisons further show largely in-phase covariability before the late 1970s but a clear post-1970s divergence, with a pronounced PDO decline concurrent with rapid wetting, suggesting that the transition toward the negative PDO phase provides an important circulation background for the recent precipitation increase in the study area. Our results provide a new annually resolved precipitation record for Northeast Asia, document historical wet–dry transitions, and help constrain the circulation mechanisms governing precipitation variability, offering a useful benchmark for regional climate assessment and prediction.