Ottawa, Canada - The amount of frozen carbon stored in the arctic and northern areas of the world is more than twice that previously estimated, increasing fears over climate change.
Large amounts of carbon are stored in frozen soils, sediments and river deltas. Carbon in permafrost is found largely in northern regions including Canada, Greenland, Kazakhstan, Mongolia, Russia, Scandinavia and the US.
"We now estimate the deposits contain over 1.5 trillion tons of frozen carbon, about twice as much carbon as contained in the atmosphere", said lead author Dr Charles Tarnocai, of Agriculture and Agri-Food Canada, Ottawa.
Dr Pep Canadell, Executive Director of the Global Carbon Project at CSIRO, Australia and co-author of the study says that the existence of these super-sized deposits of frozen carbon means that any thawing of permafrost due to global warming may lead to significant emissions of the greenhouse gases carbon dioxide and methane.
Carbon deposits frozen thousands of years ago can easily break down when permafrost thaws, releasing greenhouse gases to the atmosphere.
"Radioactive carbon dating shows that most of the carbon dioxide currently emitted by thawing soils in Alaska was formed and frozen thousands of years ago. The carbon dating demonstrates how easily carbon decomposes when soils thaw under warmer conditions," said Professor Ted Schuur, University of Florida, another co-author.
The authors point out the large uncertainties surrounding the extent to which permafrost carbon thawing could further accelerate climate change.
"Permafrost carbon is a bit of a wild card in the efforts to predict future climate change," said Dr Canadell. "All evidence to date shows that carbon in permafrost is likely to play a significant role in the 21st century climate given the large carbon deposits, the readiness of its organic matter to release greenhouse gases when thawed, and the fact that high latitudes will experience the largest increase in air temperature of all regions."
The carbon assessment is published this week in Global Biogeochemical Cycles.