Large tundra methane burst
A major concern about rising temperatures in the artic and subartcic regions is the possible effect on methane released from perennial frozen soils and peat material.
In theory biological and chemical decomposition of organic material under cold temperatures is very slow or inhibit completely – so that in millennia’s vast amounts of carcasses, peaty material and detritus has accumulated. Rising temperatures can increase decomposition, releasing the greenhouse gas methane, that itself contributes to the global warming.
A research conducted by Torben Christiansen and his research team of the University of Lund (Sweden) now has discovered that even frozen soil of the arctic tundra can release methane.They studied for two winter-months an area in the northeast of Greenland, and compared the data with measurements taken during the summer.
After the soil freeze in autumn there is an increase of methane in the air, with similar values like during the summer – an observation that now can explain the measurements of high concentrations of methane in the artic by American scientists.
The team thinks that the methane is primary produced by the microbiological activity in the active layer of the soil, then during autumn the soils freeze from up to down, squeezing the gas between holes, roots and other “tunnels” out from the underground.
The total amount of annual released gas is estimated by 30 to 100 million tons of gas, with in autumn probably 4 million of tons.
References:
MASTEPANOV et al. (2008): Large tundra methane burst during onset of freezing. Nature 456: 628-630
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When reading the post only seems Mastepanov et al., 2008 discovered the effect of methane peak at the onset of winter for the first time. While much works have been done even in the end of 1990s at Kolyma Lowland (Cherskii area) - search for works by Zimov, and Semiletov with co-authors. Unfortunately, works published in Russian still didn't reach the wide scientific society which leads to re-opening, or re-discovering. Russian Literature Group Activity in this direction tends to have invisible effect.
Actually there some findings published in English, which show the possibilities of methanogenic bacteria to generate methane at the temperature down to -15 Celsius [Rivkina et al., 2007 - FEMS Microbiol Ecol].
There is also the belief of Methane-hydrate formation in the active layer in winter, because of favorable conditions in microzones of pores under huge pressure of ice crystal growth and low temperature (down to -20 at 1 m depth). Another mechanism of methane flux in winter thus could be the frost cracking.