Climate warning as Siberia melts
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11 August 2005
·
NewScientist.com news service
·
Fred Pearce
THE world's largest frozen
peat bog is melting. An area stretching for a million square kilometres across
the permafrost of western Siberia is turning
into a mass of shallow lakes as the ground melts, according to Russian
researchers just back from the region.
The sudden melting of a bog
the size of France and Germany
combined could unleash billions of tonnes of methane, a potent greenhouse gas,
into the atmosphere.
The news of the dramatic
transformation of one of the world's least visited landscapes comes from Sergei
Kirpotin, a botanist at Tomsk State University, Russia, and Judith Marquand at the University of Oxford.
Kirpotin describes an
"ecological landslide that is probably irreversible and is undoubtedly
connected to climatic warming". He says that the entire western Siberian
sub-Arctic region has begun to melt, and this "has all happened in the
last three or four years".
What was until recently a
featureless expanse of frozen peat is turning into a watery landscape of lakes,
some more than a kilometre across. Kirpotin suspects that some unknown critical
threshold has been crossed, triggering the melting.
Western
Siberia has warmed faster than almost anywhere else
on the planet, with an increase in average temperatures of some 3 °C in the
last 40 years. The warming is believed to be a combination of man-made climate
change, a cyclical change in atmospheric circulation known as the Arctic
oscillation, plus feedbacks caused by melting ice, which exposes bare ground
and ocean. These absorb more solar heat than white ice and snow.
Similar warming has also
been taking place in Alaska: earlier this
summer Jon Pelletier of the University
of Arizona in Tucson
reported a major expansion of lakes on the North Slope fringing the Arctic Ocean.
The findings from western
Siberia follow a report two months ago that thousands of lakes in eastern Siberia have disappeared in the last 30 years, also
because of climate change (New Scientist,
11 June, p 16). This apparent contradiction arises because the two events
represent opposite end of the same process, known as thermokarsk.
In this process, rising air
temperatures first create "frost-heave", which turns the flat
permafrost into a series of hollows and hummocks known as salsas. Then as the
permafrost begins to melt, water collects on the surface, forming ponds that
are prevented from draining away by the frozen bog beneath. The ponds coalesce
into ever larger lakes until, finally, the last permafrost melts and the lakes
drain away underground.
Siberia's peat bogs
formed around 11,000 years ago at the end of the last ice age. Since then they
have been generating methane, most of which has been trapped within the
permafrost, and sometimes deeper in ice-like structures known as clathrates.
Larry Smith of the University of California, Los Angeles, estimates that the
west Siberian bog alone contains some 70 billion tonnes of methane, a quarter
of all the methane stored on the land surface worldwide.
His colleague Karen Frey
says if the bogs dry out as they warm, the methane will oxidise and escape into
the air as carbon dioxide. But if the bogs remain wet, as is the case in
western Siberia today, then the methane will
be released straight into the atmosphere. Methane is 20 times as potent a
greenhouse gas as carbon dioxide.
In May this year, Katey
Walter of the University of Alaska Fairbanks told a meeting in Washington of
the Arctic Research Consortium of the US that she had found methane hotspots in
eastern Siberia, where the gas was bubbling from thawing permafrost so fast it
was preventing the surface from freezing, even in the midst of winter.
An international research
partnership known as the Global Carbon Project earlier this year identified
melting permafrost as a major source of feedbacks that could accelerate climate
change by releasing greenhouse gases into the atmosphere. "Several hundred
billion tonnes of carbon could be released," said the project's chief
scientist, Pep Canadell of the CSIRO Division of Marine and Atmospheric
Research in Canberra, Australia.
Printed on Thu Sep 29
14:04:52 BST 2005
