Study shows sunlight, not microbes dominate CO2 production in Arctic
Just how much Arctic permafrost will thaw in the future and how fast heat-trapping carbon dioxide will be released from those warming soils is a topic of lively debate among climate scientists. To answer those questions, scientists need to understand the mechanisms that control the conversion of organic soil carbon into carbon dioxide gas. Until now, researchers believed that bacteria were largely responsible.
But in a study scheduled for online publication in Science on Aug. 21, University of Michigan researchers show for the first time that sunlight, not microbial activity, dominates the production of carbon dioxide in Arctic inland waters.
"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 same team reported in the Proceeding of the National Academy of Sciences that recently exposed carbon from thawed Alaskan permafrost is extremely sensitive to sunlight and can quickly be converted to carbon dioxide. Taken together, the two studies suggest that "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," she said.
Worldwide, permafrost soils contain twice the amount of carbon that's in the atmosphere. So thawing permafrost is a special concern for climate modelers trying to predict the timing and extent of future warming due to the ongoing buildup of carbon dioxide and other greenhouse gases.
But soil carbon does not instantly turn into carbon dioxide gas when permafrost thaws. It must be dissolved in water and chemically processed before it gets released into the atmosphere as carbon dioxide. Until now, scientists believed that bacteria were largely responsible for converting dissolved organic carbon into carbon dioxide gas in Arctic streams, lakes and rivers.
Read more at the University of Michigan.
Permafrost image via Shutterstock.