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

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 delta 13C-DIC, with averages of 7.29 +/- 0.45 mg C L-1 and -8.6 +/- 0.2 parts per thousand in summer, and 3.40 +/- 0.54 mg C L-1 and -7.4 +/- 0.6 parts per thousand in winter, respectively. Temporal variations in DIC and delta 13C-DIC were mainly controlled by carbonates weathering and silicate weathering processes. The chemical weathering reactions facilitate the consumption of dissolved CO2. Undersaturated pCO2 (120.02 +/- 29.18 mu atm) relative to atmospheric equilibrium suggests considerable capacity for CO2 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 x 10-3 Tg C-CO2 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 delta 13C-DIC values, as well as the chemical weathering-induced CO2 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 CO2 sinks and emphasizes their significance in regional carbon budgets. Maritime glacier-fed lakes play important roles in global carbon cycling; however, the dissolved inorganic carbon (DIC) source, transportation, and transition are not well-known. Here we investigated the spatiotemporal variations of DIC and identified that maritime glacier-fed lakes in the southeastern Tibetan Plateau as atmospheric carbon dioxide (CO2) sinks. We found significant temporal variations in DIC and delta 13C-DIC, primarily controlled by carbonate and silicate weathering. The glacier-fed lake system displayed tremendous CO2 uptake potential and almost 9.6 +/- 2.7 x 10-3 Tg C-CO2 was absorbed by the maritime glacier-fed lakes per year in this region. The unique landscape of the glacier-fed lake system and vulnerable weathering environment have led to the formation of CO2 sinks. With accelerated glacier retreat, more complex weathering processes will be induced, necessitating more detailed studies for further exploration in the future. Maritime glacier-fed lakes in the southeastern Tibetan Plateau are unrecognized atmospheric carbon dioxide (CO2) sinks Temporal variations of DIC and delta 13C-DIC are mainly controlled by carbonate weathering and silicate weathering The total CO2 absorbed by the maritime glacier-fed lakes in the southeastern Tibetan Plateau was 9.6 +/- 2.7 x 10-3 Tg C-CO2 yr-1