Spatiotemporal patterns of methane fluxes across alpine permafrost region on the Tibetan Plateau.

Methane (CH(4)) emissions from thawing permafrost could amplify climate warming. However, long-term trajectory of net CH(4) balance in permafrost regions, particularly high-altitude permafrost regions, remains unknown. Based on literature synthesis and CLM5.0 model, we evaluate the contemporary and future CH(4) fluxes across the Tibetan alpine permafrost region from 1989-2100. Here, we find that this permafrost region functions as a marginal CH(4) sink during 1989-2018 (-0.01 ± 0.01 Tg CH(4) yr⁻¹), and future trajectories diverge, with warming and wetting under low- and medium-emission scenarios (SSP1-2.6/SSP2-4.5) driving persistent CH(4) emissions (0.07 Tg CH(4) yr⁻¹). By contrast, under higher emission scenarios (SSP3-7.0/SSP5-8.5), the region shifts to net emissions by mid-century but enhanced atmospheric CH(4) concentrations strengthen sink, returning it to a net sink by century's end (-0.06 ~ -0.02 Tg CH(4) yr⁻¹). These results demonstrate that climate change and atmospheric CH(4) dynamics jointly mediate the trajectory of alpine permafrost CH(4) balance.