Efforts to predict future rates of climate change should include monitoring changes to the amount of wetlands in regions where permafrost is thawing, said a new study.
Permafrost — frozen ground — holds huge amounts of carbon which may be released into the atmosphere as the climate warms and the soils thaw. It is “critically important” to know where thaw is taking place and how much carbon is being exposed, the authors said.
Climate change warms northern high latitudes faster than elsewhere on Earth, which triggers permafrost to thaw. The release of permafrost carbon to the atmosphere could accelerate rates of climate change, with some estimates suggesting that potential rates of release could rival those from tropical deforestation.
If even a small proportion of the carbon is released in the form of methane, a more powerful greenhouse gas than carbon dioxide, then the feedback becomes even more significant, the authors said.
The new study, published in Nature Climate Change, measured rates of methane production from thawing peatlands in the boreal region of northern Canada.
Contrary to expectations, the study demonstrated that very little of the methane released was derived from the decomposition of ancient plant material that was previously stored in permafrost.
In fact the researchers, from the University of Exeter, University of Sussex, University of Sheffield, University of Edinburgh and other institutions in the United Kingdom and Canada observed that the large amounts of methane being produced resulted from the decomposition of new organic matter derived from the vegetation that colonized these wetlands after permafrost thawed.
“We have found the effects of permafrost thaw on methane release from northern peatlands may be driven more by changes in the extent of wetlands, than by methane produced from the decomposition of the previously-frozen organic matter itself,” Dr Iain Hartley, from the University of Exeter. “We need to improve our abilities to monitor and predict future changes in wetland extent.”
Worldwide, permafrost peatlands store approximately 20 percent of the total permafrost carbon stock which is predicted to thaw this century. The rate at which frozen organic soils could potentially decompose is up to five times greater than for frozen mineral soils, and peats are disproportionately likely to be waterlogged following thaw, the very conditions that promote methane release, the study said.
“Thaw is linked to rising temperatures, but, because vegetation and soils insulate permafrost, predictions also have to take account of climate change effects on vegetation,” said Mathew Williams of the University of Edinburgh. “Our research now has to address these complex interactions.”
Source: University of Exeter