By Alister Doyle
Oslo - Large amounts of a powerful greenhouse gas are bubbling up from a long-frozen seabed north of Siberia, raising fears of far bigger leaks that could stoke global warming, scientists said.
It was unclear, however, if the Arctic emissions of methane gas were new or had been going on unnoticed for centuries - since before the Industrial Revolution of the 18th century led to wide use of fossil fuels that are blamed for climate change.
The study said about eight million tons of methane a year, equivalent to the annual total previously estimated from all of the world's oceans, were seeping from vast stores long trapped under permafrost below the seabed north of Russia.
"Subsea permafrost is losing its ability to be an impermeable cap," Natalia Shakhova, a scientist at the University of Fairbanks, Alaska, said in a statement. She co-led the study published in Friday's edition of the journal Science.
The experts measured levels of methane, a gas that can be released by rotting vegetation, in water and air at 5 000 sites on the East Siberian Arctic Shelf from 2003-08. In some places, methane was bubbling up from the seabed.
Previously, the sea floor had been considered an impermeable barrier sealing methane, Shakhova said. Current methane concentrations in the Arctic are the highest in 400 000 years. - Reuters