Climate warming enhances chemical weathering in permafrost-dominated eastern Siberia.

Understanding the impacts of climate warming on hydrogeochemical processes, particularly in areas dominated by permafrost, is crucial. However, the natural background levels of chemical components in eastern Siberian rivers from permafrost-dominated regions and their responses to climate warming have not been adequately quantified. This study aims to address this knowledge gap by using a comprehensive river water chemistry database (n = 1264) spanning from 1940 to 2019. Our results reveal that the concentration of total dissolved solids (TDS), a key parameter of drinking water quality, in river basins predominantly free of permafrost (194.6 ± 256.4 mg/L) is approximately 2.3 times higher than in permafrost-dominated river basins (83.7 ± 35.8 mg/L) in eastern Siberia. These observations imply potential shifts in freshwater quality resulting from permafrost degradation. We further detect that carbonate weathering, which plays a fundamental role in the global carbon cycle, is a predominant process controlling hydrogeochemical cycles. (Ca + Mg) concentrations as a proxy for carbonate weathering intensity are sensitive to climate warming, increasing at a rate of 0.10 mmol/(L·°C). This finding provides evidence that the current acceleration of carbonate weathering, driven by climate warming, is already influencing local water quality. Additionally, (Ca + Mg) concentrations and TDS are highly interrelated with temperature-dependent variables (e.g., active layer thickness of permafrost and leaf area index) and basin erosion-controlling factors (e.g., precipitation, elevation and slope of basin). Under a warming climate, river chemical fluxes (e.g., export of TDS and major ions) increase notably, especially during the winter, indicating an increase in mineral-laden groundwater discharge to rivers due to permafrost degradation. Our results demonstrate that climate warming is accelerating hydrogeochemical processes in permafrost-dominated Arctic basins.