The impact of permafrost on carbon dioxide and methane fluxes in Siberia: A meta-analysis.

There are serious concerns associated with greenhouse gases (GHG) fluxes in high latitude ecosystems and how the permafrost thawing may potentially affect the global climate, through the alteration of carbon (C) dioxide (CO2) and methane (CH4) emissions. We performed a meta-analysis of 3002 observations from 104 published studies on CO2 and CH4 fluxes in Siberia (Russian Federation). Siberia is a vast region characterized by a large C-rich permafrost region, which is already degrading due to escalating climate change, and also large wetland areas, also regarded as a source of CH4. GHG fluxes were strongly controlled by location (Western, Central, Eastern, and Far East Siberia), permafrost presence and season. Maximum CO2 fluxes, in the permafrost zone, were observed in Central and Eastern Siberia. In the non-permafrost zone, maximum CO2 fluxes were found in Western Siberia. According to our analyses, CH4 fluxes in the permafrost zone were significantly different in all parts of Siberia. Thus, permafrost has a more profound effect on CH4 than on CO2 flux. The rank order of increase of CH4 emissions among the various Siberian regions is as follows: Central < Eastern < Western < Far East. In the non-permafrost area, CH4 fluxes in Western Siberia are higher than those in the Central part. Soil temperature was the only significant predictor of soil CO2 flux in the permafrost area. CH4 fluxes were well correlated with temperature and soil water content in the permafrost zone, but only dependent on temperature in the non-permafrost area. In this meta-analysis, we established several statistically significant temporal trends of long-term changes of GHG fluxes over three decades (1984-2017): an increasing trend of soil CO2 fluxes in the non-permafrost area of Western Siberia and a declining trend in the non-permafrost area of Central Siberia. There was also a significant increasing trend of CH4 fluxes in the permafrost area of Eastern Siberia, and its decreasing trend in the non-permafrost area of Western Siberia.