Russian Mountain Glaciers in a “Thawing” World: The First Estimates of the Balance of Greenhouse Gases in the Caucasus and Altai

In the modern sense, glaciers are a unique large terrestrial biome. They combine autotrophic–heterotrophic ecosystems with the most significant contribution of abiotic processes. The biome serves as an important supplier of biogenic elements and climatically active substances accumulated over glacial epochs. The cycle of biogenic greenhouse gases (GHGs) is one of the most important biospheric functions of any large ecosystem. Ablation, which is especially prominent on mountain glaciers, can have a significant impact on the GHG cycle under current warming. We have studied two mountain glaciers located in the European (North Caucasus, 2020) and Asian (Altai, 2021) parts of Russia. The purpose of this work was to estimate the current values of GHG fluxes in the influence zone of the glaciers losing their mass under warming. Due to the accumulation of cryoconites (fine-grained soils, mainly of aeolian genesis) on the ice surface, the ablation zones, on average, serve as weak sources of CO 2 for the atmosphere (15.3 mg CO 2 m –2 d –1 ), whereas the glacier accumulation zones are weak sinks (–21.5 mg CO 2 m –2 d –1 ). Young terminal moraines formed over the last 20 years are more significant additional sources of CO 2 (45.2 to 446.3 mg CO 2 m –2 d –1 ) and methane. The spatial variations in methane fluxes are highly substantial, and its contribution to radiative forcing (–0.4 to +225.6 mg CO 2 -equiv. m –2 d –1 ) may be comparable to that of CO 2 . Compared to these GHGs, the net fluxes of nitrous oxide in the glacial ecosystems studied are negligible. The contribution of soil-like bodies of young moraines significantly increases the weighted average estimation of CO 2 emission on glaciers from 2 to 1015 kg C km –2 yr –1 . The results obtained highlight the role of glaciers as preserving biospheric agents of the GHG exchange in the atmosphere.