Large amounts of methane, a significant greenhouse gas, are escaping from the sea floor off the Yamal Peninsula in Siberia as the frozen permafrost seabed thaws because of global warming, researchers say.

Off the western shore of the peninsula, methane is being released from almost 9,000 square yards of seabed, a flares of gas in some areas are flowing up to 250 feet in the water column, experts say.

"The thawing of permafrost on the ocean floor is an ongoing process, likely to be exaggerated by the global warming of the world´s oceans." says Alexey Portnov at Center for Arctic Gas Hydrate, Climate and Environment at the Arctic University of Norway.

The ocean floor permafrost is a fragile cap keeping methane trapped beneath it, a seal that is increasingly leaking, the researchers report in studies published in the Journal of Geophysical Research.

Permafrost is soil -- or sea bottom -- permanently frozen for two or more years, with no thawing between winter seasons, and is normally found in Earth's polar regions.

Continuous low ground temperatures in Siberia maintain permafrost to depths of 1,900 to 2,600 feet, but in the warming ocean off Siberia researchers have detected methane leaks at depths of no more than 100 feet, suggesting the permafrost seal on that region of the sea floor is both thin and weak.

In the ocean, permafrost is subject to a double dose of warming, Portnov explains.

"The permafrost is thawing from two sides," he says. "The interior of the Earth is warm and is warming the permafrost from the bottom up. It is called geothermal heat flux and it is happening all the time, regardless of human influence. "

Portnov has utilized mathematical modeling to calculate the degradation of seafloor permafrost since the last ice age ended.

"If the temperature of the oceans increases by two degrees as suggested by some reports, it will accelerate the thawing to the extreme," he says. "A warming climate could lead to an explosive gas release from the shallow areas."

The problem that represents for the world's climate is that methane has a disproportionately large global warming potential compared to carbon dioxide, the greenhouse gas getting the most public attention.

On a mass basis and over a time scale of a century, methane is 33 times more efficient at warming the Earth than CO2.