The sinkholes that appeared in the permafrost in Siberia this year received a great deal of media coverage around the world. The latest news is not receiving as much attention, although I think it should.
Excerpts from the article:
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The magnificent images of a crater on Yamal Peninsula, caused by collapsing permafrost, have become world famous. But did you know that this permafrost extends to the ocean floor? And it is thawing.
Credit: Image courtesy of CAGE - Center for Arctic Gas Hydrate, Climate and Environment
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“Yamal Peninsula in Siberia has recently become world famous.
Spectacular sinkholes, appeared as out of nowhere in the permafrost of the
area, sparking the speculations of significant release of greenhouse gas
methane into the atmosphere.
What is less known, is that
there is a lot of greenhouse gas methane released from the seabed offshore the
West Yamal Peninsula. Gas is released in an area of at least 7500 m2, with gas
flares extending up to 25 meters in the water column. Anyhow, there is still a
large amount of methane gas that is contained by an impermeable cap of
permafrost. And this permafrost is thawing.
"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 PhD Alexey Portnov at
Centre for Arctic Gas Hydrate, Climate and Environment (CAGE) at UiT, The
Arctic University of Norway.
It was previously proposed
that the permafrost in the Kara Sea, and other Arctic areas, extends to water
depths up to 100 meters, creating a seal that gas cannot bypass. Portnov and
colleagues have found that the West Yamal shelf is leaking, profoundly, at
depths much shallower than that.
Significant amount of gas
is leaking at depths between 20 and 50 meters. This suggests that a continuous
permafrost seal is much smaller than proposed. Close to the shore the
permafrost seal may be few hundred meters thick, but tapers off towards 20
meters water depth. And it is fragile.
"The permafrost is
thawing from two sides. 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," says Portnov.
Permafrost keeps the free
methane gas in the sediments. But it also stabilizes gas hydrates, ice-like
structures that usually need high pressure and low temperature to form.
"Gas hydrates normally
form in water depths over 300 meters, because they depend on high pressure. But
under permafrost the gas hydrate may stay stable even where the pressure is not
that high, because of the constantly low temperatures."
Gas hydrates contain huge
amount of methane gas, and it is destabilization of these that is believed to
have caused the craters on the Yamal Peninsula.”
Read full article here: http://www.sciencedaily.com/releases/2014/12/141222111559.htm
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