Glacier‐Fed Lakes Are Significant Sinks of Carbon Dioxide in the Southeastern Tibetan Plateau

Abstract Dissolved inorganic carbon (DIC) sources, transportation, and transition in inland water bodies have been intensively studied due to their important role in the global carbon cycle. While glacier‐fed lakes play a crucial role in global carbon cycling, related studies are limited. In this study, we investigated the spatiotemporal variability of DIC in the maritime glacier‐fed lakes of the southeastern Tibetan Plateau, identifying the carbon sources and potential controlling factors of DIC pathways The results revealed significant temporal variations in DIC and δ 13 C‐DIC, with averages of 7.29 ± 0.45 mg C L −1 and –8.6 ± 0.2‰ in summer, and 3.40 ± 0.54 mg C L −1 and –7.4 ± 0.6‰ in winter, respectively. Temporal variations in DIC and δ 13 C‐DIC were mainly controlled by carbonates weathering and silicate weathering processes. The chemical weathering reactions facilitate the consumption of dissolved CO 2 . Undersaturated p CO 2 (120.02 ± 29.18 μatm) relative to atmospheric equilibrium suggests considerable capacity for CO 2 uptake within glacier‐fed lakes system. We estimated that the maritime glacier‐fed lakes in the southeastern Tibetan Plateau absorb a total of 9.6 ± 2.7 × 10 −3 Tg C‐CO 2 yr −1 , highlighting their significant contribution to the global carbon budget. The distinctive landscape of the glacier‐fed system and the vulnerable weathering environment result in seasonal and spatial variations of DIC concentration and δ 13 C‐DIC values, as well as the chemical weathering‐induced CO 2 sink in glacier regions. Given the accelerated glacier retreat observed in this area, further studies on the temporal variability of DIC in the water column are urgently needed to identify the mechanisms driving the biogeochemical reactions inside glacier‐fed lake. Our study highlights the unrecognized role of maritime glacier‐fed lakes as CO 2 sinks and emphasizes their significance in regional carbon budgets.