Increased Leakage of Seabed Methane Startles Scientists
Methane release 'looks stronger'
BBCNews.com, Jan. 6, 2009
Scientists
have uncovered what appears to be a further dramatic increase in the
leakage of methane gas that is seeping from the Arctic seabed.
Methane is about 20 times more potent than CO2 in trapping solar heat.
The
findings come from measurements of carbon fluxes around the north of
Russia, led by Igor Semiletov from the University of Alaska at
Fairbanks.
"Methane release from the East Siberian Shelf is underway and it looks stronger than it was supposed [to be]," he said.
Professor
Semiletov has been studying methane seepage in the region for the last
few decades, and leads the International Siberian Shelf Study (ISSS),
which has launched multiple expeditions to the Arctic Ocean.
The preliminary findings of ISSS 2009 are now being prepared for publication, he told BBC News.
Methane seepage recorded last summer was already the highest ever measured in the Arctic Ocean.
High seepage
Acting as
a giant frozen depository of carbon such as CO2 and methane (often
stored as compacted solid gas hydrates), Siberia's shallow shelf areas
are increasingly subjected to warming and are now giving up greater
amounts of methane to the sea and to the atmosphere than recorded in
the past.
This undersea permafrost was until recently considered to be stable.
But now scientists think the release of such a powerful greenhouse gas may accelerate global warming.
Higher
concentrations of atmospheric methane are contributing to global
temperature rise; this in turn is projected to cause further permafrost
melting and the release of yet more methane in a feedback loop.
A
worst-case scenario is one where the feedback passes a tipping point
and billions of tonnes of methane are released suddenly, as has
occurred at least once in the Earth's past.
Such
sudden releases have been linked to rapid increases in global
temperatures and could have been a factor in the mass extinction of
species.
According
to a report by the US National Oceanic and Atmospheric Administration
(Noaa), the springtime air temperature across the region in the period
2000-2007 was an average of 4C higher than during 1970-1999.
That is the fastest temperature rise on the planet, claims the university.
The
recent thaw over the last decade means that some of the large reserve
of carbon from organic material such as dead animals and plants in
sediments is now being released into the sea and into our atmosphere.
Previously it was thought much of this gas was absorbed into the sea.
But
according to a recent report that Professor Semiletov and his team
compiled for the environmental group WWF, the shallow depth of arctic
shelves means that methane is reaching the atmosphere without reacting
to become CO2 dissolved in the ocean.
Professor
Semiletov's fellow researcher aboard the Russian icebreaker that
carries the ISSS team each year is Professor Orjan Gustafsson from
Stockholm University in Sweden.
He said
that methane measured in the atmosphere around the region is 100 times
higher than normal background levels, and in some cases 1,000 times
higher.
'No alarm'
Despite
the high readings, Professor Gustafsson said that so far there was no
cause for alarm, and stressed that further studies were still necessary
to determine the exact cause of the methane seepage.
"It is important now to understand how fast it is being released and how much is being released," he said.
However, there is a real fear that global warming may cause Siberia's subsea permafrost to thaw.
Some
estimates put the amount of carbon trapped in shelf permafrost at 1,600
billion tonnes - roughly twice as much carbon as in the atmosphere now.
The
release of this once captive carbon from destabilised ocean sediments
and permafrost would have catastrophic effect on our climate and life
on Earth, warn the scientists.
METHANE HYDRATES
* Methane gas is trapped inside a crystal structure of water-ice
* The gas is released when the ice melts, normally at 0C
* At higher pressure, i.e., under the ocean, hydrates are stable at higher temperatures
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