2011 - Cooperative Institute for Research in Environmental Sciences ...

Tingjun Zhang
Degrading Permafrost on the
Qinghai-Xizang (Tibet) Plateau
The Qinghai-Xizang
(Tibet) Plateau has an
average elevation of
greater than 4,000 m above
sea level (a.s.l.) and is
known as “The Roof of
The World.” As a result,
permafrost is well-developed
over the majority of
the plateau’s area. Due
to the impacts of climate
warming and human activities,
such as the newly
constructed Qinghai-Tibet
Railroad, permafrost on
the plateau is experiencing
significant warming and
degradation during the
past few decades. Changes
in permafrost conditions
would have dramatic impact on local and regional ecosystems,
hydrological and carbon cycles, landscape and, more
importantly, engineering infrastructure. In collaboration
with Prof. Qingbai Wu and his colleagues from the Cold and
Arid Regions Environmental and Engineering Research Institute,
Chinese Academy of Sciences, we established in the
past few years a long-term permafrost-monitoring network,
which is still expanding, along the Qinghai-Xizang (Tibet)
Railroad (Figure 1).
The preliminary results indicate that among the 28
monitoring sites along the network, average active-layer
thickness is about 3.1 m with a range from about 1.2 m to 4.9
m (Figure 2). From 2006 through 2010, active-layer thickness
has increased at a rate of about 6.3 cm/year. Permafrost
temperature at the depth of zero amplitude (i.e., mean annual
ground temperature, MAGT) ranges from about -3.0°C
to -0.1°C (Figure 2). Although permafrost along the network
is relatively warm, permafrost temperature at the depth of
zero amplitude is increasing at a rate of about 0.01°C per
year over the past five years. The magnitude of permafrosttemperature
increase is greater for relatively colder permafrost
(MAGT of less than -1.0°C) than for relatively warm
permafrost (MAGT less than -1.0°C). This is consistent with
observations in the Arctic, primarily due to the effect of
latent heat as unfrozen water content increases with permafrost
temperature increase. This permafrost monitoring will
continue for the next 10 years.
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Figure 1:
(a) Site elevation;
(b) mean annual
ground temperature
(MAGT) at
depth of zero
amplitude;
and (c) active
layer thickness
(ALT) along the
Qinghai-Xizang
(Tibet) Railroad.
CIRES Annual Report 2011 59