NASA is continuing a multi-year study which, so far, is demonstrating that Arctic permafrost is warming more rapidly than the air. In a release this week the situation in the Arctic is referred to as the "canary in the coal mine" for climate change.
The extreme conditions in the Arctic prevent decomposition of most plant and animal material. Each year there is a partial thaw which allows vegetation to grow, which then dies and is added to the permafrost when the colder weather returns. The result is thousands of years of stored organic material. The report notes:
"...Arctic permafrost soils have accumulated vast stores of organic carbon - an estimated 1,400 to 1,850 petagrams of it (a petagram is 2.2 trillion pounds, or 1 billion metric tons). That's about half of all the estimated organic carbon stored in Earth's soils. In comparison, about 350 petagrams of carbon have been emitted from all fossil-fuel combustion and human activities since 1850. Most of this carbon is located in thaw-vulnerable topsoils within 10 feet (3 meters) of the surface."
The concern is that as the permafrost warms the carbon stores may be released as CO2 and/or methane.
"It's important to accurately characterize the soils and state of the land surfaces. There's a strong correlation between soil characteristics and release of carbon dioxide and methane. Historically, the cold, wet soils of Arctic ecosystems have stored more carbon than they have released. If climate change causes the Arctic to get warmer and drier, scientists expect most of the carbon to be released as carbon dioxide. If it gets warmer and wetter, most will be in the form of methane.
The distinction is critical. Molecule per molecule, methane is 22 times more potent as a greenhouse gas than carbon dioxide on a 100-year timescale, and 105 times more potent on a 20-year timescale. If just one percent of the permafrost carbon released over a short time period is methane, it will have the same greenhouse impact as the 99 percent that is released as carbon dioxide. "