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Permafrost melt to boost atmospheric CO2 faster than thought
The more CO2, the more global warming; the more global warming, the more CO2
A new study has shown that melting Arctic permafrost will "release climate-warming carbon dioxide gas into the atmosphere much faster than previously thought," the University of Michigan warns.
"In this research, we provide the first evidence that the respiration of previously frozen soil carbon will be amplified by reactions with sunlight and their effects on bacteria," said Rose Cory of the University of North Carolina when announcing the publication of her team's research in a paper published in the Proceedings of the National academy of Science (PNAS).
Cory, along with George Kling of the University of Michigan and their research colleagues, studied "thermokarst failures" – places where melting permafrost has exposed carbon-rich soil – in Arctic Alaska to discover how exposure to sunlight affected the conversion of carbon buried in the previously frozen soil into atmosphere-warming CO2.
The answer: a lot. In boffinary terms, as the paper explains, "Our results suggest that photostimulation will rapidly (days to months) increase conversion to CO2 by an additional 40 per cent or more in thawed and released C compared with that remaining in the dark."
Sunlight's UV rays, it turns out, not only degrade organic soil carbon into CO2, but also alters the carbon into a form that makes it yummy to bacteria. When bacteria feed upon it, they exhale CO2 – well, "respire" would be more correct – thus releasing more of that earth-warming gas into the atmosphere.
The increase of atmospheric of CO2, of course, creates a positive feedback loop: the more heat-trapping CO2 in the atmosphere, the more the planet heats; the more the planet heats, the more permafrost collapses into thermokarst failures; the more thermokarst failures, the more exposed carbon that sunlight can transform into CO2 – which is added to the atmosphere, and 'round and 'round we go.
According to one recent model, the contribution of melting permafrost to atmospheric CO2 would likely continue even if fossil-fuel CO2 contributions suddenly ceased – which, of course, is vanishingly unlikely – due to the aforementioned positive feedback loop.
Cory and Kling's key finding is the role of sunlight in the permafrost cycle. "Until now," Kling said, "we didn't really know how reactive this ancient permafrost carbon would be – whether it would be converted into heat-trapping gases quickly or not."
Now we know. ®