Fig. 1: Field observations of thermokarst lakes during ice-covered period on the Tibetan Plateau.
a Distribution of the 56 monitored thermokarst lakes during ice-covered period (this study) and 162 thermokarst lakes during ice-free period18. A total of 409 field observations were conducted from June 2019 to April 2023. Permafrost and vegetation distribution data are sourced from existing distribution dataset12,69. b–e The images depict field observations during the ice-covered periods from March to April, captured by P. L and M. M. f Density frequency of dissolved CH4 concentrations and their comparison between the ice-covered period and ice-free period. The lines indicate CH4 concentrations of individual samples during ice-free and ice-covered periods. g The relationships of dissolved CH4 concentrations between the ice-covered and ice-free periods under vegetation types of alpine swamp meadow (ASM), alpine meadow (AM), alpine steppe (AS) and alpine desert (AD). Notably, the circles represent the individual lakes observed during both the ice-free and ice-covered periods. The corresponding values indicate the average CH₄ concentration within the same lake during the two periods. The shaded area represents the 95% confidence interval. *P < 0.05, **P < 0.01, ***P < 0.001.
