Steve Conner, The Independent
The first evidence that millions
of tons of a greenhouse gas 20 times more potent than carbon dioxide is being
released into the atmosphere from beneath the Arctic seabed has been discovered
by scientists.
The Independent has been passed
details of preliminary findings suggesting that massive deposits of sub-sea
methane are bubbling to the surface as the Arctic region becomes warmer and its
ice retreats.
Underground stores of methane
are important because scientists believe their sudden release has in the past
been responsible for rapid increases in global temperatures, dramatic changes to
the climate, and even the mass extinction of species. Scientists aboard a
research ship that has sailed the entire length of Russia's northern coast have
discovered intense concentrations of methane--sometimes at up to 100 times
background levels--over several areas covering thousands of square miles of the
Siberian continental shelf.
In the past few days, the
researchers have seen areas of sea foaming with gas bubbling up through
"methane chimneys" rising from the sea floor. They believe that the
sub-sea layer of permafrost, which has acted like a "lid" to prevent
the gas from escaping, has melted away to allow methane to rise from
underground deposits formed before the last ice age.
They have warned that this is
likely to be linked with the rapid warming that the region has experienced in
recent years.
Methane is about 20 times more
powerful as a greenhouse gas than carbon dioxide and many scientists fear that
its release could accelerate global warming in a giant positive feedback where
more atmospheric methane causes higher temperatures, leading to further
permafrost melting and the release of yet more methane.
The amount of methane stored
beneath the Arctic is calculated to be greater than the total amount of carbon
locked up in global coal reserves, so there is intense interest in the
stability of these deposits as the region warms at a faster rate than other
places on earth.
Orjan Gustafsson of Stockholm
University in Sweden, one of the leaders of the expedition, described the scale
of the methane emissions in an email exchange sent from the Russian research
ship Jacob Smirnitskyi.
"We had a hectic finishing
of the sampling programme yesterday and this past night," said Dr
Gustafsson. "An extensive area of intense methane release was found. At
earlier sites we had found elevated levels of dissolved methane. Yesterday, for
the first time, we documented a field where the release was so intense that the
methane did not have time to dissolve into the seawater but was rising as
methane bubbles to the sea surface. These 'methane chimneys' were documented on
echo sounder and with seismic [instruments]."
At some locations, methane
concentrations reached 100 times background levels. These anomalies have been
seen in the East Siberian Sea and the Laptev Sea, covering several tens of
thousands of square kilometres, amounting to millions of tons of methane, said
Dr Gustafsson. "This may be of the same magnitude as presently estimated
from the global ocean," he said. "Nobody knows how many more such areas
exist on the extensive East Siberian continental shelves.
"The conventional thought
has been that the permafrost 'lid' on the sub-sea sediments on the Siberian
shelf should cap and hold the massive reservoirs of shallow methane deposits in
place. The growing evidence for release of methane in this inaccessible region
may suggest that the permafrost lid is starting to get perforated and thus leak
methane... The permafrost now has small holes. We have found elevated levels of
methane above the water surface and even more in the water just below. It is
obvious that the source is the seabed."
The Arctic region as a whole has
seen a 4C rise in average temperatures over recent decades and a dramatic
decline in the area of the Arctic Ocean covered by summer sea ice. Many scientists
fear that the loss of sea ice could accelerate the warming trend because open
ocean soaks up more heat from the sun than the reflective surface of an
ice-covered sea.
