Perilous Times and
Climate Change
20 May 2012 Last updated at 12:54 ET
Rapid Arctic melt releasing ancient methane
By Richard Black Environment correspondent, BBC News
Many of the sites were bubbling methane that has been stored for
millennia
Scientists have identified thousands of sites in the Arctic where
methane that has been stored for many millennia is bubbling into
the atmosphere.
The methane has been trapped by ice, but is able to escape as the
ice melts.
Writing in the journal Nature Geoscience, the researchers say this
ancient gas could have a significant impact on climate change.
Methane is the second most important greenhouse gas after CO2 and
levels are rising after a few years of stability.
There are many sources of the gas around the world, some natural
and some man-made, such as landfill waste disposal sites and farm
animals.
Tracking methane to these various sources is not easy.
But the researchers on the new Arctic project, led by Katey Walter
Anthony from the University of Alaska at Fairbanks (UAF), were
able to identify long-stored gas by the ratio of different
isotopes of carbon in the methane molecules.
Using aerial and ground-based surveys, the team identified about
150,000 methane seeps in Alaska and Greenland in lakes along the
margins of ice cover.
Local sampling showed that some of these are releasing the ancient
methane, perhaps from natural gas or coal deposits underneath the
lakes, whereas others are emitting much younger gas, presumably
formed through decay of plant material in the lakes.
"We observed most of these cryosphere-cap seeps in lakes along the
boundaries of permafrost thaw and in moraines and fjords of
retreating glaciers," they write, emphasising the point that
warming in the Arctic is releasing this long-stored carbon.
"If this relationship holds true for other regions where
sedimentary basins are at present capped by permafrost, glaciers
and ice sheets, such as northern West Siberia, rich in natural gas
and partially underlain by thin permafrost predicted to degrade
substantially by 2100, a very strong increase in methane carbon
cycling will result, with potential implications for climate
warming feedbacks."
Atmospheric methane concentration is rising again after a plateau
of a few years
Quantifying methane release across the Arctic is an active area of
research, with several countries despatching missions to monitor
sites on land and sea.
The region stores vast quantities of the gas in different places -
in and under permafrost on land, on and under the sea bed, and -
as evidenced by the latest research - in geological reservoirs.
"The Arctic is the fastest warming region on the planet, and has
many methane sources that will increase as the temperature rises,"
commented Prof Euan Nisbet from Royal Holloway, University of
London, who is also involved in Arctic methane research.
"This is yet another serious concern: the warming will feed the
warming."
How serious and how immediate a threat this feedback mechanism
presents is a controversial area, with some scientists believing
that the impacts will not be seen for many decades, and others
pointing out the possibility of a rapid release that could swiftly
accelerate global warming.