Aaron Hoover
Permafrost blanketing the northern hemisphere contains more than twice the amount of carbon in the atmosphere, making it a potentially mammoth contributor to global climate change depending on how quickly it thaws.
So concludes a group of nearly two dozen scientists in a paper in the journal Bioscience in September. The lead author is Ted Schuur, an associate professor of ecology at the University of Florida.
Previous studies by Schuur and his colleagues elsewhere have estimated the carbon contained in permafrost in northeast Siberia. The new research expands that estimate to the rest of the permafrost-covered northern latitudes of Russia, Europe, Greenland and North America. The estimated 1,672 billion metric tons of carbon locked up in the permafrost is more than double the 780 billion tons in the atmosphere today.
“It’s bigger than we thought,” Schuur said.
Permafrost is frozen ground that contains roots and other soil organic matter that decompose extremely slowly. When it thaws, bacteria and fungi break down carbon contained in this organic matter much more quickly, releasing it to the atmosphere as carbon dioxide or methane, both greenhouse gases.
Scientists have become increasingly concerned about this natural process as temperatures in the world’s most northern latitudes have warmed.
Two years ago, Schuur and two colleagues authored a paper in the journal Science estimating that 400,000 square miles of northeast Siberian permafrost contained 500 billion metric tons of carbon. For this new paper, scientists combined an extensive database of measurements of carbon content in different types of permafrost soils with the estimated spatial extent of those soils in Russia, Europe, Greenland and North America.
The new estimate is important because it mirrors other climate change science, suggesting that at a certain tipping point, natural processes could contribute significant amounts of greenhouse gases, supplementing human-influenced, industrial processes that release fossil fuel carbon, Schuur said.
“There are relatively few people living in the permafrost zone,” Schuur said. “But we could have significant emissions of carbon from thawing permafrost in these remote regions.”
The research was conducted as part of the International Polar Year 2008-2009 and sponsored by the National Science Foundation-funded National Center for Ecological Analysis and Synthesis, and the United Nations Educational, Scientific and Cultural Organization in a grant to the Global Carbon Project.