Carbon Dioxide Dominates Greenhouse Gases Generated By Arctic's Thawing Permafrost


Temperatures in the Arctic rise twice faster than anywhere else in the world, and as the planet continues to heat up, the permafrost, or the frozen ground, in the region melts.

The thawing poses a problem because frozen soil contains nearly twice the amount of carbon present in the atmosphere. The greenhouse gas methane (CH4), which is 34 times more potent than carbon dioxide, is also released from melting permafrost.

How Melting Of Permafrost Releases Greenhouse Gases

As permafrost thaws, bacteria that were frozen in it wake up and start to digest the remains of ancient animals and plants that were stored as carbon in the soil. The process produces either carbon dioxide or methane.

Permafrost Carbon Feedback Loop

The ratio of the two gases produced by the melting of the permafrost can influence the strength of the so- called permafrost carbon feedback loop, or the warming-thawing-more warming cycle, wherein the planet warming greenhouse gases that are released because of melting permafrost cause rise in temperatures which lead to more thawing and carbon release.

Ratio Of Carbon To Methane

In a new study published in the journal Nature Climate Change, scientists looked into the ratio of carbon to methane released by thawing permafrost.

Christina Schädel, from Northern Arizona University, and colleagues analyzed carbon release from 25 Arctic soil incubation studies to better understand the conditions that promote the release of either of the two greenhouse gases and eventually identified the soil's temperature and availability of oxygen.

The meta-analysis showed that drier and aerobic soils release more carbon compared with wetter and anaerobic soils. The same goes true with a 10 degrees Celsius increase in soil temperature.

"Under aerobic incubation conditions, soils released 3.4 (95% CI, 2.2 to 5.2) times more C than under anaerobic conditions," the researchers wrote in the study published on June 13.

"Even when accounting for the higher heat trapping capacity of CH4, soils released 2.3 (95% CI, 1.5 to 3.4) times more C under aerobic conditions."

Schädel and colleagues also found that most of the carbon comes in the form of carbon dioxide, Methane only makes up 5 percent of the total anaerobic products, which means that even though it is the more potent planet-warming gas, the small quantity released relative to carbon dioxide in anaerobic conditions makes wet soils of less concern than dry soils.

"We conclude that the permafrost carbon feedback will be stronger when a larger percentage of the permafrost zone undergoes thaw in a dry and oxygen-rich environment," Schädel said.

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