Methane release from thawing northern peatlands less than predicted

Thawing permafrost soils at northern high latitudes could release massive amounts of carbon to the atmosphere. The effect on the Earth’s climate depends strongly on the proportion of this carbon that is released as the more powerful greenhouse gas methane (CH4) rather than carbon dioxide (CO2). In northern peatlands, thawing of permafrost causes surface subsidence and water-logging which exposes  previously frozen organic matter to low-oxygen conditions – ideal conditions for CH4 release. However, a recent study shows that although substantial CH4 releases were recorded from thawing peatlands in northern Canada, only a small amount was derived from old, previously frozen, carbon. Most of the CH4 release was derived from the decomposition under low-oxygen conditions of recently deposited organic material. It is concluded that thaw-induced changes in surface wetness and wetland area, rather than the decomposition old carbon, may determine the effect of permafrost thaw on CH4 emissions from northern peatlands. Limited contribution of permafrost carbon to methane release from thawing peatlands, Mark D. A. Cooper et al., Nature Climate Change (2017), Published online 26 June 2017, doi:10.1038/nclimate3328