| Frozen depositories are giving up
methane to the sea Scientists have uncovered what appears to be a further
dramatic increase in the leakage of methane gas that is seeping from the
Arctic seabed. ... Methane is about 20 times more potent than
CO2 in trapping solar heat. ... The findings come
from measurements of carbon fluxes around the north of Russia, led by Igor
Semiletov from the University of Alaska at Fairbanks.
... "Methane release from the East Siberian Shelf is
underway and it looks stronger than it was supposed [to be]," he
said. ... Professor Semiletov has been
studying methane seepage in the region for the last few decades, and leads
the International Siberian Shelf Study (ISSS), which has launched multiple
expeditions to the Arctic Ocean. ...
The preliminary findings of ISSS 2009 are now being prepared for
publication, he told BBC News. ... Methane
seepage recorded last summer was already the highest ever measured in the
Arctic Ocean. ... High seepage Acting as a
giant frozen depository of carbon such as CO2 and methane (often stored as
compacted solid gas hydrates), Siberia's shallow shelf areas are
increasingly subjected to warming and are now giving up greater amounts of
methane to the sea and to the atmosphere than recorded in the
past. ... METHANE HYDRATES Methane gas is trapped
inside a crystal structure of water-ice The gas is released when the ice
melts, normally at 0C At higher pressure, ie under the ocean, hydrates are
stable at higher temperatures This undersea permafrost was until recently
considered to be stable. ... But now scientists
think the release of such a powerful greenhouse gas may accelerate global
warming. ... Higher concentrations of
atmospheric methane are contributing to global temperature rise; this in
turn is projected to cause further permafrost melting and the release of
yet more methane in a feedback loop. ... A
worst-case scenario is one where the feedback passes a tipping point and
billions of tonnes of methane are released suddenly, as has occurred at
least once in the Earth's past. ... Such
sudden releases have been linked to rapid increases in global temperatures
and could have been a factor in the mass extinction of
species. ... According to a report by
the US National Oceanic and Atmospheric Administration (Noaa), the
springtime air temperature across the region in the period 2000-2007 was
an average of 4C higher than during 1970-1999.
... That is the fastest temperature rise on the planet,
claims the university. ... The
recent thaw over the last decade means that some of the large reserve of
carbon from organic material such as dead animals and plants in sediments
is now being released into the sea and into our
atmosphere. ... Trapped below
that is the methane hydrate now warming and leaking through holes in the
defrosting sediments. ... 1. Methane
hydrate is stable at high pressure and low temperature 2. Nearer the
surface, where water pressure is lower, hydrates break down earlier than
at greater depth as temperatures rise 3. Gas rises from the sea-bed in
plumes of bubbles - some of it dissolves before it reaches the surface 4.
The ISSS team says it has detected methane breaking the ocean
surface. ...
Previously it was thought much of this gas was absorbed into the
sea. ... But according to
a recent report that Professor Semiletov and his team compiled for the
environmental group WWF, the shallow depth of arctic shelves means that
methane is reaching the atmosphere without reacting to become CO2
dissolved in the ocean. ... Professor
Semiletov's fellow researcher aboard the Russian icebreaker that carries
the ISSS team each year is Professor Orjan Gustafsson from Stockholm
University in Sweden. ... He
said that methane measured in the atmosphere around the region is 100
times higher than normal background levels, and in some cases 1,000 times
higher. ... 'No
alarm' ... Despite the high readings,
Professor Gustafsson said that so far there was no cause for alarm, and
stressed that further studies were still necessary to determine the exact
cause of the methane seepage. ...
"It is important now to understand how fast it is being released and
how much is being released," he said.
... However, there is a real fear that global warming
may cause Siberia's subsea permafrost to thaw.
... Some estimates put the amount of carbon trapped in
shelf permafrost at 1,600 billion tonnes - roughly twice as much carbon as
in the atmosphere now. ... The release
of this once captive carbon from destabilised ocean sediments and
permafrost would have catastrophic effect on our climate and life on
Earth, warn the scientists. |