Carbon budgets of lakes on the Tibetan Plateau: Highlighting non-negligible carbon emissions from small lakes

• The CO 2 emission fluxes of lakes on the Tibetan Plateau from 2016 to 2021 were estimated. • The relatively higher CO 2 emission fluxes from small lakes compared to their surface area ratios on the Tibetan Plateau were emphasized. • Both the ice-free and ice-covered periods were taken into account in the carbon budgets. • CO 2 emission mechanisms from lakes of different sizes on the Tibetan Plateau during the ice-free and ice-covered periods are discussed. The release of carbon dioxide (CO 2 ) from lakes is a critical element of carbon (C) emissions from inland waters. Within the realm of climate change, the inquiries surrounding whether lakes on the Tibetan Plateau (TP) function as C sources or sinks and the magnitude of CO 2 exchange flux from these lakes have garnered significant attentions. Nevertheless, accurately assessing the lakes’ contribution to the C budgets poses challenges due to data scarcity and methodological inaccuracies. By amalgamating data from literature reviews and field measurements for different sizes of lakes during the ice-free (IF) and ice-covered (IC) periods from 2016 to 2021, this study offers a refined estimate of the CO 2 exchange flux and flux rate for lakes on the TP by including lakes ranging in size from 0.01 to 1 km 2 (small lakes) in the C budgets. Findings revealed that the annual CO 2 exchange flux of TP lakes amounted to 7.10 Tg C yr –1 , with 6.56 Tg C yr –1 and 0.54 Tg C yr –1 during the IF and IC periods, respectively. Notably, small lakes contributed 0.76 Tg C yr –1 , representing 10.65 % of the total lake CO 2 emissions on the TP, which indicates the significant role of small lakes in estimating CO 2 emissions from TP lakes. The CO 2 exchange fluxes of small lakes showed significant variability during the IF period, with the origins of lake water replenishment possibly explaining this diversity, where glacial meltwater replenishment is likely a key contributing factor. In contrast, CO 2 emissions from small lakes increased during the IC period. The view of this study is that the groundwater recharge with higher CO 2 concentrations and the shallow nature of small lakes may be the main reasons for the increase in CO 2 emissions from small lakes during this period. The study underscores that the contribution of small lakes to the CO 2 budgets of TP lakes is substantial and warrants attention, particularly in elucidating the mechanisms driving CO 2 emissions from small lakes.