Geoscience Reference
In-Depth Information
of permafrost, which exists at high eleva-
tions in mountain ranges (e.g., the Andes)
at mid latitudes. Permafrost may be
con-
tinuous
, meaning that it is present every-
where with minor exceptions, or
discontinu-
ous
, scattered about in patches. As a rule it
stops groundwater flow and inhibits plant
growth.
On top of the permafrost is a thin active
layer a few feet thick, which thaws during
the summer and allows the growth of a few
species of plants. As permafrost melts and
the active layer increases in thickness, plant
diversity also increases. Plants flourishing
in the new conditions may include bushes
that can shade the surface and slightly re-
duce the rate of melting. The more diverse
flora will increase the uptake of CO
2
from
the atmosphere, but not at a rate that will
counteract the newly released gases (as we
noted earlier, primarily methane) from de-
caying organic matter. Animal populations
are also affected by permafrost, because
the hard ice restricts burrowing for dens.
So reduction of permafrost may result in
significant changes in the ecosystem.
Construction on permafrost requires
special care to avoid melting, which causes
the loss of strength and volume of the sur-
face layer. Where melting has occurred,
buildings have tilted, stands of trees have
become “drunken forests,” and roads and
railroad tracks have collapsed. Of particu-
lar concern in China is the recently con-
structed Tibetan Plateau railroad, a proj-
ect costing $4 billion and extending over
1,118 kilometers (695 miles), half of which
is built on permafrost. Buildings in the
Arctic are commonly built on pilings or
on a three- to six-foot (one- to two-meter)
layer of gravel. The Alaskan oil pipeline
uses insulated pipes suspended above the
ground between closely spaced towers to
protect the pipeline from the fluctuations
of the frozen ground. Melting permafrost
also causes landslides in mountain regions
and very extensive retreat of Arctic Ocean
shorelines.
The most important global impact of
shrinking permafrost is the release of meth-
ane and carbon dioxide (chapter 1). As per-
mafrost melts, gas which was stored in bub-
bles in the ice is released, and even more
gas is produced by the decay of long-frozen
organic matter. In the Arctic, methane is
also found as methane hydrates (frozen
methane), which are held in place by the
weight of the overlying impermeable ice in
the permafrost zone. Although methane
hydrates on land in the Arctic are much less
voluminous than the same deposits on the
sea floor, their release by melting perma-
frost could significantly add to the green-
house gases released from permafrost.
Myths, Misinterpretations, and
Misunderstandings of the Deniers
myth
: Scientists in need of funding invent
reports of increased melting of permafrost.
Maria Leibman of the Earth Criosphere
Institute in Russia denies that greenhouse
gases affect the climate, and in a common
