The exploration of the spatiotemporal distribution of greenhouse gas (GHG) exchange in the cryosphere (including ice sheet, glaciers, and permafrost) is important for understanding its future feedback to the atmosphere. Mountain glaciers and ice sheets may be potential sources of GHG emissions, but the magnitude and distribution of GHG emissions from glaciers and ice sheets remain unclear because observation data are lacking. In this study, in situ CH 4 and CO 2 and the mixing ratios of their carbon isotope signatures in the air inside an ice cave were measured, and CH 4 and CO 2 exchange in the meltwater of Laohugou glacier No. 12, a high-mountain glacier in an arid region of western China, was also analyzed and compared with the exchange in downstream rivers and a reservoir. The results indicated elevated CH 4 mixing ratios (up to 5.7 ppm) and depleted CO 2 (down to 168 ppm) in the ice cave, compared to ambient levels during field observations. The CH 4 and CO 2 fluxes in surface meltwater of the glacier were extremely low compared with their fluxes in rivers from the Tibetan Plateau (TP). CH 4 and CO 2 mixing ratios in the air inside the ice cave were mainly controlled by local meteorological conditions (air temperature, wind speed and direction) and meltwater runoff. The carbon isotopic compositions of CH 4 and CO 2 in the ice cave and terminus meltwater indicated 6 13 C-CH 4 depletion compared to ambient air, suggesting an acetate fermentation pathway. The abundances of key genes for methanogenic archaea/genes encoding methyl coenzyme M reductase further indicated the production of CH 4 by methanogenic archaea from the subglacial meltwater of high -mountain glaciers. The discovery of CH 4 emissions from even small high -mountain glaciers indicates a more prevalent characteristic of glaciers to produce and release CH 4 from the subglacial environment than previously believed. Nevertheless, further research is required to understand the relationship between this phenomenon and glacial dynamics in the third pole.

来源平台：SCIENCE OF THE TOTAL ENVIRONMENT