Dissolved carbon variability in alpine river catchments of the central Tibetan Plateau

Alpine rivers rapidly transport large-stored dissolved carbon (DC) from glaciers and alpine permafrost to downstream aquatic ecosystems. The Tibetan Plateau (TP) is an extraordinarily high-altitude region with ubiquitous alpine rivers undergoing intensified changes due to climate changes. However, the potential impacts on the magnitude and properties of DC in alpine rivers still remain poorly understood. Here, we examined the spatio-temporal variability of DC concentrations and properties across 14 alpine rivers in the central TP. Based on monthly investigations conducted during the open water season, the average concentration of dissolved organic carbon (DOC) and inorganic carbon (DIC) in TP alpine rivers was 1.03 ± 0.73 and 14.73 ± 13.05 mg L −1 , respectively. The aromatic degree of dissolved organic matter (DOM) was relatively high with mean SUVA 254 of 4.18 ± 1.52 L mg C −1 m −1 . Moreover, DOC export rate was found more intensive in glacier fed streams (0.017 ± 0.015 g C km −2 s −1 ) was found than nonglacier fed rivers (0.009 ± 0.011 g C km −2 s −1 ). Multiple regression models indicate that riverine DC concentrations were overwhelmingly elevated by vegetation coverage within the subbasins. In the glacier recharging catchments, inputs of summer glacier meltwater significantly enhanced terrigenous humic-like DOM (with higher SUVA 254 ) flushing, which caused nearly constant riverine DOM over seasons. In contrast, nonglacier fed rivers were characterized by a sharp decline in DOM during the post monsoon season. These findings suggest a future scenario of heightened terrestrial leaching and riverine export of DC, driven by the expansion of vegetations and increased glacier derived DOM subsidy under ongoing climate warming and wetting on the TP. • Vegetation coverage is vital for dissolved carbon export in alpine rivers on the central TP. • The seasonal variability of fluvial DOC exhibited marked divergence between glacier and nonglacier fed rivers. • Glacier meltwater accelerates the high aromatic DOM flushing to headwater streams.