Sunlight stimulates release of carbon dioxide in melting permafrost – ‘Permafrost carbon is potentially a huge factor that will help determine how fast the Earth warms’
By Monte Morin
12 February 2013 (Los Angeles Times) – Ancient plant and animal matter trapped within Arctic permafrost can be converted rapidly into climate-warming carbon dioxide when melted and exposed to sunlight, according to a new study. In a report published Monday in the Proceedings of the National Academy of Sciences, a team of environmental and biological scientists examined 27 melting permafrost sites in Alaska and found that bacteria converted dissolved organic carbon materials into the greenhouse gas CO2 40% faster when exposed to ultraviolet light. Study authors said that while it remained unclear just how much CO2 would be released as Arctic permafrost continues to melt, the findings were cause for concern. High latitude soils currently store twice the amount of carbon than is found in the atmosphere. “What we can say now is that regardless of how fast the thawing of the Arctic permafrost occurs, the conversion of this soil carbon to carbon dioxide and its release into the atmosphere will be faster than we previously thought,” senior author George Kling, a University of Michigan ecologist and aquatic biogeochemist, said in a statement. “That means permafrost carbon is potentially a huge factor that will help determine how fast the Earth warms,” Kling said. [more]
Sunlight stimulates release of carbon dioxide in melting permafrost
ABSTRACT: Recent climate change has increased arctic soil temperatures and thawed large areas of permafrost, allowing for microbial respiration of previously frozen C. Furthermore, soil destabilization from melting ice has caused an increase in thermokarst failures that expose buried C and release dissolved organic C (DOC) to surface waters. Once exposed, the fate of this C is unknown but will depend on its reactivity to sunlight and microbial attack, and the light available at the surface. In this study we manipulated water released from areas of thermokarst activity to show that newly exposed DOC is >40% more susceptible to microbial conversion to CO2 when exposed to UV light than when kept dark. When integrated over the water column of receiving rivers, this susceptibility translates to the light-stimulated bacterial activity being on average from 11% to 40% of the total areal activity in turbid versus DOC-colored rivers, respectively. The range of DOC lability to microbes seems to depend on prior light exposure, implying that sunlight may act as an amplification factor in the conversion of frozen C stores to C gases in the atmosphere.
Surface exposure to sunlight stimulates CO2 release from permafrost soil carbon in the Arctic
