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 Methane bubbling from Siberian thaw lakes!

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InläggRubrik: Methane bubbling from Siberian thaw lakes!   sön okt 07, 2007 12:21 am

Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming

Citat :
K. M. Walter1, S. A. Zimov2, J. P. Chanton3, D. Verbyla4 and F. S. Chapin, III1

Large uncertainties in the budget of atmospheric methane, an important greenhouse gas, limit the accuracy of climate change projections1, 2. Thaw lakes in North Siberia are known to emit methane3, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia.

We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated3. Extrapolation of these fluxes indicates that thaw lakes in North Siberia emit 3.8 teragrams of methane per year, which increases present estimates of methane emissions from northern wetlands (< 6–40 teragrams per year; refs 1, 2, 4–6) by between 10 and 63 per cent.

We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260–42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.


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InläggRubrik: Sv: Methane bubbling from Siberian thaw lakes!   sön okt 07, 2007 12:23 am

A methane feedback from the past strikes again

Bogs, not oceans, may have been the source of an increase in atmospheric methane

Citat :
What triggered the Palaeocene-Eocene thermal maximum (PETM) about 55 million years ago, which saw the fastest period of warming documented in Earth's geological history? The PETM is associated with a rapid rise in greenhouse gases, particularly methane -- but the big question is where did the methane come from?

The most common answer has been the ocean (methane hydrates), but new research in Nature casts doubt on the ocean theory -- instead finding chemical evidence that the methane came from terrestrial sources, bogs, which were themselves stimulated by rising temperatures -- an amplifying feedback. The lead author says:


Senast ändrad av den sön okt 07, 2007 12:26 am, ändrad totalt 1 gång
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InläggRubrik: Sv: Methane bubbling from Siberian thaw lakes!   sön okt 07, 2007 12:23 am

More about methan in permafrost

Citat :
The report explains that rising temperatures, coupled with the thawing of frozen land or permafrost, are leading to the creation of new and expansion of existing lakes in places such as Siberia, which are releasing bubbles of methane, estimated to be 43,000 years old.
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InläggRubrik: Sv: Methane bubbling from Siberian thaw lakes!   sön okt 07, 2007 3:46 am

Another feedback mechanism in the Arctic.

Citat :
The research team has reported the extraordinary warming of the soil in Svalbard during the winter of 2005-2006. The abstract mentions in passing that such events, if they continue into the future, will have ‘potentially damaging’ effects on permafrost. Why does this matter?

The matter at issue is methane. Looking recently at the surface temperature anomalies over huge areas of Central and Northern Siberia, with numbers exceeding +5C for sustained periods, there is an implication that what was observed at Svalbard (albeit in Winter) also holds true for very large areas where permafrost currently exists. Just last year, researchers at the University of Fairbanks, Alaska, reported that methane release from permafrost degradation and the creation of lakes in tundra might be as much as five times higher than previously estimated. I cannot find any current numbers on atmospheric methane, or on emissions levels from Siberia, and we may well have to wait until the CDIAC or another agency publishes its annual summary early next year before we have the actual numbers. My guess is that they will show a rise in concentrations.
Geophysical Research Letters.
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InläggRubrik: Sv: Methane bubbling from Siberian thaw lakes!   Idag på 3:29 am

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