The layer just below the Earth's surface is teeming with microbes capable of altering composition of the atmosphere.
Whether they do so or not all depends on the availability of organic matter in the soil, which in turn depends on whether that soil is frozen or not.
In the Arctic, where, thanks to global warming, permafrost is failing to live up to its name, more organic material is becoming available, and this could spell even more global warming.
Using a permafrost sample from the region, an international group of researchers studied the changes in the composition of organic matter within the soil that alters the ratio between methane and carbon dioxide produced by anaerobic microbes present within the subsurface, eventually boosting the concentration of greenhouse gases within the atmosphere. The study appeared in a paper titled "Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production," published in the journal Proceedings of the National Academy of Sciences.
To start with, frozen soil -- which is composed largely of peat -- starts thawing. The layer of soil then collapses, and the portion underneath -- where a huge chunk of permafrost used to sit earlier -- is now inundated with water, says Jeff Chanton, an environmental scientist with the John Widmer Winchester Professor of Oceanography at Florida State, who was involved in the study.
The water contains organic matter, which is degraded by anaerobic bacteria to produce carbon dioxide and methane. Initially the amount of carbon dioxide produced is more than that of methane. But with time, the characteristic of the organic matter changes in a way that boosts the production of methane much more than that of carbon dioxide.
Production of both the substances increase, but the relative ratio between the two changes from 10:1 to 1:1, says Dr. Chanton.
The activities also give way to the production of specific vegetation. "It's like clear cutting a forest," says Chanton. First sphagnum mosses colonize the area. Then sedges start growing in the region. These plants act as conduits for releasing the methane -- which is produced at the subsurface -- into the atmosphere.
“[T]he associated changes in plant community composition in the polar regions could lead to way more carbon being released into the atmosphere as methane," Chanton said in a press release.
Methane -- a more powerful greenhouse gas -- is 33 times more effective in heating the Earth than carbon dioxide.
“The world is getting warmer, and the additional release of gas would only add to our problems,” he said in a press release.