Ancient Permafrost Quickly Turns into Carbon Dioxide after Thawing

Ancient Low–molecular-weight Organic Acids in Permafrost Fuel Rapid Carbon Dioxide Production upon Thaw
Proceedings of the National Academy of Sciences (Published online before print October 26, 2015, doi: 10.1073/pnas.1511705112) / by Travis W. Drake, et al.
http://www.pnas.org/content/early/2015/10/21/1511705112

[From Press Release] Researchers from the U.S. Geological Survey and key academic partners have quantified how rapidly ancient permafrost decomposes upon thawing and how much carbon dioxide is produced in the process.
Huge stores of organic carbon in permafrost soils ­­— frozen for hundreds to tens of thousands of years across high northern latitudes worldwide — are currently isolated from the modern day carbon cycle. However, if thawed by changing climate conditions, wildfire, or other disturbances, this massive carbon reservoir could decompose and be emitted as the greenhouse gases carbon dioxide and methane, or be carried as dissolved organic carbon to streams and rivers…

At a newly excavated tunnel operated by the U.S. Army Corps of Engineers near Fairbanks, Alaska, a research team from USGS, the University of Colorado Boulder, and Florida State University set out to determine how rapidly the dissolved organic carbon from ancient (about 35,000 years old) “yedoma” soils decomposes upon soil thaw and how much carbon dioxide is produced…

“It had previously been assumed that permafrost soil carbon this old was already degraded and not susceptible to rapid decomposition upon thaw,” said Kim Wickland, the USGS scientist who led the team.

The researchers found that more than half of the dissolved organic carbon in yedoma permafrost was decomposed within one week after thawing. About 50% of that carbon was converted to carbon dioxide, while the rest likely became microbial biomass…

These rates are among the fastest permafrost decomposition rates that have been documented. It is the first study to link rapid microbial consumption of ancient permafrost soil-derived dissolved organic carbon to the production of carbon dioxide.

An important implication of the study for aquatic ecosystems is that dissolved organic carbon released by thawing yedoma permafrost will be quickly converted to carbon dioxide and emitted to the atmosphere from soils or small streams before it can be transported to major rivers or coastal regions. ..

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