As the Arctic warms, thawing permafrost will release greenhouse gases faster and in greater amounts than previously believed.
It will release as much carbon as deforestation, say the researchers - and the effect on climate will be two and a half times greater, because emissions include methane, which has a greater effect on warming than carbon dioxide.
University of Florida researcher Edward Schuur and University of Alaska Fairbanks graduate student Benjamin Abbott, combined data from previous models with expert opinion on what percentage of the surface permafrost is likely to thaw, how much carbon will be released and how much of that carbon will be in the form of methane.
They estimate that the amount of carbon released by 2100 will be 1.7 to 5.2 times larger than reported in recent modeling studies, which used a similar warming scenario.
"The larger estimate is due to the inclusion of processes missing from current models and new estimates of the amount of organic carbon stored deep in frozen soils," says Abbott.
"There’s more organic carbon in northern soils than there is in all living things combined; it’s kind of mind boggling."
Most large-scale models assume that permafrost warming depends on how much the air above the permafrost is warming. Missing from the models, say Schuur and Abbott, are processes such as the effects of abrupt thawing that can melt an ice wedge, resulting in collapsed ground and accelerating additional thawing.
"We know about a lot of processes that will affect the fate of arctic carbon, but we don’t yet know how to incorporate them into climate models," says Abbott.
"We’re hoping to identify some of those processes and help the models catch up."