Methane emissions from thermokarst lakes must emphasize the ice-melting impact on the Tibetan Plateau.

Abstract

Thermokarst lakes, serving as significant sources of methane (CH₄), play a crucial role in affecting the feedback of permafrost carbon cycle to global warming. However, accurately assessing CH₄ emissions from these lakes remains challenging due to limited observations during lake ice melting periods. In this study, by integrating field surveys with machine learning modeling, we offer a comprehensive assessment of present and future CH₄ emissions from thermokarst lakes on the Tibetan Plateau. Our results reveal that the previously underestimated CH₄ release from lake ice bubble and water storage during ice melting periods is 11.2 ± 1.6 Gg C of CH₄, accounting for 17 ± 4% of the annual total release from lakes. Despite thermokarst lakes cover only 0.2% of the permafrost area, they annually emit 65.5 ± 10.0 Gg C of CH₄, which offsets 6.4% of the net carbon sink in alpine grasslands on the plateau. Considering the loss of lake ice, the expansion of thermokarst lakes is projected to lead to 1.1-1.2 folds increase in CH₄ emissions by 2100. Our study allows foreseeing future CH₄ emissions from the rapid expanding thermokarst lakes and sheds new lights on processes controlling the carbon-climate feedback in alpine permafrost ecosystems.