Chemical weathering in glacial catchment acting as a net carbon source

Over geological time scales, continental silicate weathering is considered as a critical carbon sink that regulates long-term climate feedback. By contrast, recent studies indicate that sulfide oxidation during weathering can be as a potential carbon source. However, whether chemical weathering in glacial conditions characterized by extreme erosion is a net carbon sink or source remains elusive. Here, we present the seasonal carbon cycle processes in a typical glacier catchment, via high-resolution (weekly) river water sampling during the whole 2017 in the Laohugou river, northeastern Tibetan Plateau. Our seasonal result shows that the release of CO2 by sulfide oxidation during the monsoon period can be much faster than CO2 consumption through weathering of silicate rocks, with maximum of ∼26 times. Extending to global glacial basins, we observed a consistent pattern that inorganic carbon releases in alpine glaciers are faster than atmospheric CO2 consumption. We propose that weathering in global glacial environment acts as a significant carbon source, and thus affects climate feedback. [Display omitted] •Seasonal water composition and sources of contributing endmembers in Laohugou river are identified.•SO42− in Laohugou river is 30 times higher than Cl−.•Significant carbon release (maximum of 26.1 times than its consumption) occurs during the monsoon season.•Weathering in Laohugou catchment acts as a net carbon source.•Global inland alpine glaciers are proposed as a net carbon source.