Synergistic effects of interdecadal oscillations in dual ocean basins trigger pronounced annual runoff variability in cell-based reconstructions during the late 20th century, and the impact of runoff changes on the ecological and agro-pastoral

Study region For this study, the Taoer River basin located in mid-high latitude cold mountainous area was selected as the research object. Long-term runoff evolution of this watershed exerts profound impacts on regional ecological security and agro-pastoral economic development. Unraveling centennial runoff patterns and drivers is critical for cold-region water governance. Study focus This study innovatively reconstructs annual runoff using birch xylem cell wall thickness chronology for the first time in the mid-high latitude cold zone. We systematically disentangle runoff driving forces from three dimensions: external radiative forcing, ocean boundary signals, and cross dual-ocean basin ocean-atmosphere coupling oscillations, and further quantify the ecological and economic consequences of historical runoff fluctuations. The outcomes provide scientific support for water resource allocation, extreme hydrological risk early warning, and coordinated eco-agricultural sustainable development in analogous cold basins. New hydrological insights for the region Synergistic oscillations of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) dominate amplified late-20th-century runoff variability in the Taoer Basin, the core innovation corresponding to this paper’s title. Our 328-year reconstruction identifies the 1843–1872 dry phase and two wet periods (1936–1961), with short-term runoff governed by ENSO (El Niño–Southern Oscillation). Runoff correlates negatively with solar radiation and positively with northwest Pacific SST. Snow-permafrost melt creates pre-2000 positive temperature-runoff linkage, reversed by modern evapotranspiration. Extreme wet runoff sharply cuts crop output but barely hurts livestock production.