Scientists previously thought that Arctic permafrost was converted into carbon dioxide by a process of bacteria. However, this may not be the case, a new study suggests. Sunlight can produce this change in the Arctic soil known as permafrost.
This has a huge impact on climate change research, because the release of carbon dioxide from the Arctic region is one of the major contributors of carbon dioxide to the environment.
"Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth -- and equals an amount twice of that in the atmosphere," said Byron Crump, one of the co-authors of the study. "This represents a major change in thinking about how the carbon cycle works in the Arctic."
Crump is an Oregon State University microbial ecologist.
Rose Cory, the lead author on the paper, explains that for the soil permafrost to turn into carbon dioxide two things must happen: first, the permafrost must thaw a bit and then bacteria must convert the carbon into carbon dioxide or methane. Most of this process is accomplished in the soil, but a significant amount of carbon flows off into natural bodies of water nearby like lakes.
"It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2," Cory said. "This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling."
She said that scientists hoping to understand more about the process of greenhouse gas emission must consider both the effects of sunlight and the bacteria, not one or the other in isolation. If only the bacteria are considered, it will lead to the wrong answer, she said.
The researchers analyzed the speed at which bacteria and light from the sun turned carbon into carbon dioxide from all bodies of water in the Alaskan Arctic. They said that the processes could be different depending on the body of water, because each water source has a different level of bacteria activity and sunlight.
They found that for most of the freshwater bodies of water they found, sunlight converted soil into carbon dioxide faster than bacteria.
"This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river -- and most lakes -- so that no dissolved organic carbon is kept in the dark," Crump said.
