By Steve Connor, The Independent, December 13, 2011
Dramatic and unprecedented plumes of methane – a
greenhouse gas 20 times more potent than carbon dioxide – have been seen
bubbling to the surface of the Arctic Ocean by scientists undertaking an
extensive survey of the region.
The scale and volume of the methane release has
astonished the head of the Russian research team who has been surveying the
seabed of the East Siberian Arctic Shelf off northern Russia for nearly 20
years.
In an exclusive interview with The Independent, Igor
Semiletov, of the Far Eastern branch of the Russian Academy of Sciences, said
that he has never before witnessed the scale and force of the methane being
released from beneath the Arctic seabed.
"Earlier we found torch-like structures like this
but they were only tens of metres in diameter. This is the first time that
we've found continuous, powerful and impressive seeping structures, more than
1,000 metres in diameter. It's amazing," Dr Semiletov said. "I was
most impressed by the sheer scale and high density of the plumes. Over a
relatively small area we found more than 100, but over a wider area there
should be thousands of them."
Scientists estimate that there are hundreds of millions
of tonnes of methane gas locked away beneath the Arctic permafrost, which
extends from the mainland into the seabed of the relatively shallow sea of the
East Siberian Arctic Shelf. One of the greatest fears is that with the
disappearance of the Arctic sea-ice in summer, and rapidly rising temperatures
across the entire region, which are already melting the Siberian permafrost,
the trapped methane could be suddenly released into the atmosphere leading to
rapid and severe climate change.
Dr Semiletov's team published a study in 2010 estimating
that the methane emissions from this region were about eight million tonnes a
year, but the latest expedition suggests this is a significant underestimate of
the phenomenon.
In late summer, the Russian research vessel Academician
Lavrentiev conducted an extensive survey of about 10,000 square miles of sea
off the East Siberian coast. Scientists deployed four highly sensitive
instruments, both seismic and acoustic, to monitor the "fountains" or
plumes of methane bubbles rising to the sea surface from beneath the seabed.
"In a very small area, less than 10,000 square
miles, we have counted more than 100 fountains, or torch-like structures,
bubbling through the water column and injected directly into the atmosphere
from the seabed," Dr Semiletov said. "We carried out checks at about
115 stationary points and discovered methane fields of a fantastic scale – I
think on a scale not seen before. Some plumes were a kilometre or more wide and
the emissions went directly into the atmosphere – the concentration was a
hundred times higher than normal."
Dr Semiletov released his findings for the first time
last week at the American Geophysical Union meeting in San Francisco.
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