Tree-ring-derived April–July drought variability in the western Loess Plateau of China over the last four centuries and its linkage to the Atlantic Multidecadal Oscillation

Short instrumental records limit assessment of long-term drought variability on the western Loess Plateau of China. In this paper, we reconstructed April–July self-calibrating Palmer Drought Severity Index (scPDSI) variability for the last four centuries (1610–2016 CE) using a tree-ring width chronology obtained from Pinus tabuliformis in the Kongtong Mountains. Tree growth was strongly moisture limited, and the chronology was most strongly correlated with April–July scPDSI ( r = 0.74, p < 0.01). A linear regression model explained 55.3% of the instrumental scPDSI variance during 1950–2016 CE. The reconstruction identified five persistent drought periods and five pluvial periods, with 1991–2011 CE showing the lowest mean scPDSI among the persistent drought intervals. BEAST analysis of the 11-year-smoothed series detected major regime shifts around 1731, 1761, 1777, 1934, and 1990 CE. Spectral analysis revealed pronounced interannual and multidecadal variability. Reconstructed scPDSI showed a significant negative correlation with the Atlantic Multidecadal Oscillation (AMO), while atmospheric circulation and wave-activity-flux diagnostics were consistent with an Atlantic–Eurasian pathway linking warm North Atlantic conditions to drought-favorable circulation over the western Loess Plateau. ENSO was also associated with warm-season moisture variability: scPDSI anomalies were significantly negative during El Niño years, whereas positive anomalies during La Niña years were not statistically significant. These results extend the regional hydroclimatic record and provide a long-term perspective on regional drought variability associated with multidecadal North Atlantic and interannual tropical Pacific variability.