Unraveling scale-dependent flood responses to changing climate extremes over the Tibetan Plateau

Understanding the dynamic interplay between floods and climate extremes in the Tibetan Plateau has long been constrained by scale fragmentation. Here, we elucidate the scale-dependent responses using historical observations and modelling. The average flood day and annual maximum daily discharge are governed by two complementary pathways: atmospheric input and catchment modulation. Spatially, flood drivers shift from cryosphere control in the west to monsoon control in the east. Crucially, low-order tributaries are dominated by the atmospheric source mechanism, responding instantaneously to high-intensity precipitation, while catchment modulators play a more important role in high-order mainstems. Furthermore, cross-watershed analysis further underscores that upstream temperature changes contribute 4.0% to downstream flood frequency and 6.4% to magnitude variability via hydrological connectivity. The scale-specific disparities, shaped by the synergistic effects of watershed hydrological processes, underlying surface heterogeneity, climate factor sensitivities, and climate-cryosphere interactions, establish a framework for alpine flood attribution and predictive models. Terrestrial water fluxes on the Tibetan Plateau respond to climate change in uniquely scale-dependent ways shaped by its geography and geomorphology, as shown through analyses of historical observations and modelling.