New research suggests sunlight, not bacteria, is responsible for most of the carbon dioxide in Arctic inland waters.
The findings could help researchers better-understand the mechanisms that control the conversion of organic soil carbon into carbon dioxide gas, the University of Michigan reported. In the past researchers though bacteria were largely responsible for this process.
"Our results suggest that sunlight, rather than biological processes, controls the fate of carbon released from thawing permafrost soils into Arctic surface waters," said aquatic geochemist Rose Cory, first author of the Science paper and an assistant professor in the U-M Department of Earth and Environmental Sciences.
Last year the researchers reported recently-exposed carbon from thawed Alaska permafrost can be quickly converted to carbon dioxide when exposed to sunlight.
"We're likely to see more carbon dioxide released from thawing permafrost than people had previously believed," Cory said."We're able to say that because we now know that sunlight plays a key role and that carbon released from thawing permafrost is readily converted to carbon dioxide once it's exposed to sunlight."
Permafrost soil contains about twice as much carbon as is in its atmosphere, and how fast it melts has a major influence on climate change; looking at this solid could help researchers predict the future of our climate. Soil carbon does not instantly turn into carbon dioxide when permafrost thaws, first it must be dissolved in water and chemically processed; in the past researchers believed bacteria were primarily responsible for this conversion.
To make their findings the researchers looked at water samples from 135 lakes and 73 rivers on the North Slope of Alaska. They compared sunlight induced carbon precessing (photodegradation) to carbon conversion via bacteria.
They found photodegradation of carbon exceeded bacterial respiration about 19-fold; it accounted for between 70 and 90 percent of the observed carbon conversion.
"Carbon in thawing permafrost soils may have global impacts on climate change, yet controls on its processing and fate have been poorly understood," said study co-author George Kling, a professor in the U-M Department of Ecology and Evolutionary Biology. "Our study shows that photochemical processing of soil carbon is an important, newly measured component of the Arctic carbon budget."
The findings were published Aug. 21 in the journal Science.
