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Melting permafrost methane emissions: Another threat to climate change
15 September 2006
A frozen peat bog covering the entire sub-Arctic area of Western Siberia, the size of France and Germany, contains billions of tonnes of greenhouse gas that is melting for the first time since it was sequestered more than 11,000 years ago before the end of the last ice age.
Researchers Sergei Kirpotin of Tomsk State University in Siberia, and Judith Marquand of Oxford University first reported in 2005 that one million square kilometres of permafrost had started to melt.
Such an unprecedented thaw could dramatically increase the rate of global warming.
A study published in the September 7th issue of Nature authored by Katey Walter of the University of Alaska, and Jeff Chanton of Florida State University reports that greenhouse gas is escaping into the atmosphere at a frightening rate.
Global warming gases trapped in the soil are being released from thawing permafrost at five times the rate previously thought. Researchers warn it may set off a climate change time bomb.
With a more accurate method of measuring methane bubbling from two Siberian thaw lakes, the researchers revealed the world's northern tundra as a much larger source of methane release.
New calculations show the levels of methane emissions from northern wetlands 10 to 63 percent higher than the previous estimates. |
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When Siberian permafrost melts, carbon buried since the Pleistocene era is bubbling to the surface of lakes, and dissipating into the atmosphere as methane, a greenhouse gas 23 times more potent than carbon dioxide. |
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Researchers have studied a unique Siberian permafrost called yedoma which is a frozen tundric dust, deposited during the last glacial age. It is rich in biomass such as plant roots and animal bones, with a carbon content 10 to 30 times higher than average deep soils.
When organic matter decomposes in air, the gas produced escapes as carbon dioxide. However much of the yedoma in Siberia lies at the bottom of thaw lakes, and when it decomposes under water, provides microbes with feedstock that produce methane.
Methane is a much more potent greenhouse gas than carbon dioxide, but it has a shorter life of about a decade. Ultimately it oxidizes to become carbon dioxide which then stays in the atmosphere for more than a hundred years.
The study of greenhouse gases released from land is exceedingly complex because soils vary considerably.
It has been known for some time that a huge amount of organic carbon is trapped in Siberian tundra. The more plentiful yedoma is a vast reservoir of carbon that has been neglected in most analyses of climate change.
An estimated 500 gigatons of carbon have been flash frozen in yedoma regions, and 900 gigatons in permafrost worldwide. This large store would more than double the amount of carbon in the atmosphere today if it is released.
Thousands of lakes in eastern Siberia have disappeared during the last 30 years. This apparent contradiction is because the two events represent opposite ends of the same process called thermokarsk.
Higher air temperatures first create frost-heave, transforming flat permafrost into hollows and hummocks known as salsas. As the permafrost melts, water collects on the surface, forming ponds that do not drain because of the frozen bog beneath. The ponds combine into larger lakes until the last permafrost melts and the lakes drain underground. |
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The vicious cycle of methane release and warming ..... taking climate change towards the tipping point .....
It is feared that Siberia's thawing lake region, which comprises 90 percent of the Russian permafrost zone, will release methane into the atmosphere at a rate that will overwhelm human actions to curtail carbon dioxide emissions.
As the permafrost thaws as a result of global warming caused by increasing atmospheric carbon dioxide, large quantities of methane are released. When methane gets out it causes more warming in a vicious cycle, and the release of even more methane, and so it goes on. Scientists refer to this as a positive feedback loop. |
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Siberia is one of the fastest warming regions on Earth - average temperatures have increased 3°C in the last 40 years. |
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Chris Field, director of global ecology at the Carnegie Institution of Washington, says "that's the thing that is scary about this whole thing. There are lots of mechanisms that tend to be self-perpetuating and relatively few that tend to shut it off."
Sergei Kirpotin of Tomsk State University describes permafrost melting as an "ecological landslide that is probably irreversible". He says the entire western Siberian sub-Arctic region has begun to melt in the last three or four years.
Larry Smith of the University of California Los Angeles, has estimated that the western Siberian bog alone contains 70 billion tonnes of methane, which is 25 percent of all methane stored on the land surface worldwide. |
Siberian warming is believed to be a result of man-made climate change, a cyclical change in atmospheric circulation known as the Arctic oscillation, together with feedbacks caused by melting ice. Exposure of darker bare ground and ocean absorb a greater amount of solar heat than white ice and snow.
Scientific findings in Siberia are a strong reminder to governments worldwide that it is clearly evident that immediate, massive reductions in global warming gas emissions into the atmosphere are needed, to prevent runaway, irreversible climate change.
It has been known that feedbacks could exacerbate global warming. However, it had been assumed that these changes would occur when warming was more advanced.
Permafrost thaw, polar ice reduction, and tropical rainforest drought are major climate change events that are occurring sooner and at a greater pace than previously predicted. It is a strong indicator that the world is running out of time.
More rapid warming has also been occurring in Alaska. In 2005 Jon Pelletier of the University of Arizona reported a major expansion of lakes on the North Slope adjoining the Arctic Ocean.
Vladimir Romanovsky, who is geophysics professor at the University of Alaska at Fairbanks, said the big methane or carbon dioxide release hasn't started yet, but it is coming. In Alaska and Canada where there is much less permafrost than Siberia, it is closer to happening, he said. |
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Thawing permafrost will accelerate global warming
