The methane time bomb
Steve Connor
Arctic scientists discover new global
warming threat as melting permafrost releases millions of tons of a gas
20 times more damaging than carbon dioxide
T10he 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 preliminary findings of the International Siberian Shelf Study
2008, being prepared for publication by the American Geophysical Union,
are being overseen by Igor Semiletov of the Far-Eastern branch of the
Russian Academy of Sciences. Since 1994, he has led about 10 expeditions
in the Laptev Sea but during the 1990s he did not detect any elevated
levels of methane. However, since 2003 he reported a rising number of
methane "hotspots", which have now been confirmed using more sensitive
instruments on board the Jacob Smirnitskyi.
Dr Semiletov has suggested several possible reasons why methane is
now being released from the Arctic, including the rising volume of
relatively warmer water being discharged from Siberia's rivers due to
the melting of the permafrost on the land.
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.
Source: Independent News and Media limited |