Latitudinal gradients in runoff dynamics across undisturbed Eurasian permafrost rivers under accelerating climate change

Abstract

While the impacts of permafrost degradation on Eurasian river discharge are well-documented, a systematic understanding of how these impacts vary across latitudes—critical for predicting continental water security and Arctic freshwater export—remains lacking. This study bridges this gap by analyzing latitudinal gradients in extreme and mean monthly discharges—lowest (LD), mean (MD), and highest (HD) monthly discharge—across 22 major Eurasian permafrost rivers, integrating snowmelt dynamics and winter river ice dynamics with watershed energy-water budgets. We find pronounced latitudinal gradients in hydrological responses. The most robust change is a pan-Eurasian increase in winter baseflow (LD, 5%–8% per decade), primarily driven by warming-induced river ice (24-d shorter freezing duration; 8.2% volume decline contributing 19.6% to LD rise). In contrast, high (HD) and mean (MD) discharge trends show distinct zonal divergence: significant increases in precipitation-driven low latitudes, a post-1990s reversal from decline to increase in mid-latitudes, and muted but more variable trends in high latitudes where precipitation increases are offset by evapotranspiration and storage changes. The late 1990s marked a critical shift, synchronizing abrupt hydrological changes with contemporaneous shifts in regional climate forcing and cryospheric processes. The identified latitudinal patterns and their underlying mechanisms provide a predictive framework for anticipating future hydrological extremes—from winter water scarcity to flood risks—in these vulnerable basins in a warming world.