Methane, a gas 20 times more potent than carbon dioxide in trapping heat in the atmosphere, appears to be bubbling up from thawing permafrost at a rate five times faster than originally measured, scientists reported Wednesday.
The effect, reported in this week's issue of the journal Nature, is seen mostly in Siberia in a type of carbon-rich permafrost that was flash frozen about 40,000 years ago. A new, more accurate measuring technique found that methane bubbling from that permafrost under Siberian lakes was higher than previously recorded.
“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.”
The researchers measured methane in two northern Siberia lakes. “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 percent,” the researchers wrote.
Scientists are fretting about a global warming cycle that had not been part of their gloomy climate forecasts: Warming already under way thaws permafrost, soil that had been continuously frozen for thousands of years.
Thawed permafrost releases methane and carbon dioxide. Those gases reach the atmosphere and help trap heat on Earth in the greenhouse effect. The trapped heat thaws more permafrost, and so on.
'A more vicious cycle'
“The higher the temperature gets, the more permafrost we melt, the more tendency it is to become a more vicious cycle,” said Chris Field, director of global ecology at the Carnegie Institution of Washington. “That’s the thing that is scary about this whole thing. There are lots of mechanisms that tend to be self-perpetuating and relatively few that tends to shut it off.”
Another study earlier this summer in the journal Science
Another study earlier this summer in the journal Sciencefound that the amount of carbon trapped in this type of permafrost — called yedoma — is much more prevalent than originally thought and 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 the methane and carbon dioxide will escape the soil if temperatures increase, scientists say.
The issue of methane and carbon dioxide released from permafrost has caused concern this summer among climate scientists and geologists. Specialists in Arctic climate are coming up with research plans to study the effect, which is not well understood or observed, said Robert Corell, chairman of the Arctic Climate Impact Assessment, a group of 300 scientists.
'Slow-motion time bomb'
“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 Science study. “There’s these big surprises out there that we don’t even know about.”
Most of this yedoma is in north and eastern Siberia, areas that until recently had not been studied at length by scientists.
Scientists aren’t quite sure which is worse. Methane is far more powerful in trapping heat, but only lasts about a decade before it dissipates into carbon dioxide and other chemicals. Carbon dioxide traps heat for about a century.
“The bottom line is it’s better if it stays frozen in the ground,” Schuur said. “But we’re getting to the point where it’s going more and more into the atmosphere.”
Vladimir Romanovsky, a geophysics professor at the University of Alaska at Fairbanks, said he thinks the big methane or carbon dioxide release hasn’t started yet, but it’s coming. It’s closer in Alaska and Canada, which only has a few hundred square miles of yedoma, he said.
In Siberia, the many lakes of melted water make matters worse because the water, although cold, helps warm and thaw the permafrost, Walter said.
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