Gases escaping permafrost alarm scientists
The Associated Press, Sept. 6, 2006
WASHINGTON - Global warming gases trapped in the soil are bubbling out of thawing permafrost in amounts far higher than previously thought and may trigger what researchers warn is a climate time bomb.
Methane - a greenhouse gas 23 times more powerful than carbon dioxide - is being released from permafrost at a rate five times faster than thought, according to a study being published today in the journal Nature. The findings are based on new, more accurate measuring techniques.
"The effects can be huge," said lead author Katey Walter of the University of Alaska at Fairbanks. "It's coming out a lot and there's a lot more to come out."
Scientists worry about a vicious global warming cycle that was not part of their already-gloomy climate forecast: Warming already under way thaws permafrost, soil that has been frozen for thousands of years. Thawed permafrost releases methane and carbon dioxide. Those gases reach the atmosphere and help trap heat on Earth. The trapped heat thaws more permafrost, and the cycle continues.
Some scientists say the cycle is already under way, but others disagree.
Most of the methane-releasing permafrost is in Siberia. Another study earlier this summer in the journal Science found that the amount of carbon trapped in this type of permafrost - called yedoma - may be 100 times the amount of carbon released into the air each year by the burning of fossil fuels.
It won't all come out at once or even over several decades, but if temperatures increase, then the methane and carbon dioxide will escape the soil, scientists say.
The permafrost issue has caused a quiet buzz of concern among climate scientists and geologists. Specialists on the Arctic climate are coming up with research plans to study the permafrost effect, which is not well understood or observed, said Robert Corell, chairman of the Arctic Climate Impact Assessment, a study group of 300 scientists.
"It's kind of like a slow-motion time bomb," said Ted Schuur, a professor of ecosystem ecology at the University of Florida and co-author of the study in Science.
Most of the yedoma is in little-studied areas of northern and eastern Siberia. What makes that permafrost special is that much of it lies under lakes; the carbon below gets released as methane. Carbon beneath dry permafrost is released as carbon dioxide.
Using special underwater bubble traps, Walter and her colleagues found giant hot spots of bubbling methane that were never measured before because they were hard to reach.
"I don't think it can be easily stopped; we'd really have to have major cooling for it to stop," Walter said.
Copyright 2006 Associated Press
Nature 443, 71-75(7 September 2006) | doi:10.1038/nature05040; Received 5 December 2005; Accepted 3 July 2006
Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming
Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections1,2. Thaw lakes in North Siberia are known to emit methane3, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated3. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 640 teragrams per year; refs 1, 2, 46) by between 10 and 63 per cent. We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,26042,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.
Received 5 December 2005 | Accepted 3 July 2006