Environmental Engineering Reference
In-Depth Information
soil, such as peat bogs, will produce methane as it decomposes. This
could have a major effect on climate. The volume of methane that
may be produced as the permafrost melts is about the same amount
that is released annually from the world's wetlands and agriculture.
It would double the level of the gas in the atmosphere, leading to a
10 to 25 percent increase in global warming, another positive feedback
loop.
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In addition, as the permafrost thaws, it reveals bare ground, and
bare ground warms up more quickly than refl ective ice, accelerating
the rate of thawing—a positive feedback loop. As noted earlier, north-
ern climates warm faster than temperate ones even without the added
effect of melting permafrost. It is noteworthy that western Siberia,
an area with extensive permafrost, is heating up faster than anywhere
else in the world, having experienced a rise of about 5ºF in the past
forty years.
Permafrost under the Arctic Ocean is also melting, and in many areas,
methane is bubbling up from the ocean fl oor. The amount of methane
stored there has been calculated to be greater than the total amount of
carbon in global coal reserves.
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A methane time bomb may be lurking
beneath the Arctic Ocean that has not been factored into existing climate
models.
The thawing of the world's permafrost has been described by Sergei
Kirpotin, a Russian ecologist, as an ecological landslide that is probably
irreversible. He says that the entire western Siberian sub-Arctic region
has begun to melt, and this has all happened since 2000. A featureless
expanse of frozen peat is turning into a watery landscape of lakes, some
several thousand feet in diameter. Kirpotin suspects that a critical thresh-
old has been crossed, triggering the rapid melting.
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American scientists have reported a major expansion of lakes on the
North Slope fringing the Arctic Ocean. Many of the permafrost lakes
eventually disappear, because as the depth of thawing increases, the
water is able to drain away underground.
As permafrost thaws and porous soil takes its place, the velvety carpet
of moss and lichen is replaced by shrub bushes and eventually forests.
The trees and shrubs will then accelerate warming because dark vegeta-
tion absorbs more solar radiation—another positive feedback loop.
Although these higher plants absorb carbon dioxide from the atmo-
sphere, the warming effect of a forested landscape far outweighs the
cooling from the carbon dioxide uptake.
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