Geology Reference
In-Depth Information
of reports and special journal issues are now available (e.g. Boer and Koster, 1992; Brown
et al., 2000; Harris and Haeberli, 2003; Harris et al., 2001; Koster, 1993; Nelson, 2004;
Rachold, 1999; Rachold et al., 2003; Weller and Anderson, 1998).
Not surprisingly, recent research has concentrated upon measurement of the cry-
ospheric parameters likely to be sensitive to climate change. These include the depth of
the active layer, the thermal condition of permafrost, the extent and duration of seasonal
snow cover, and the freeze-up and break-up of lakes and rivers. Emphasis is also placed
upon quantitative long-term studies that document the frequency and magnitude of cryo-
genic processes that are controlled, to varying degrees, by climatic factors. These proc-
esses include thermal-contraction cracking, thermokarst activity, active-layer slope
failures, and solifl uction movement.
15.2. CLIMATE CHANGE AND PERMAFROST
A recent simulation from the US National Center for Atmospheric Research (NCAR)
examined the state of permafrost within a global climate model that includes interactions
among the atmosphere, ocean, land, sea ice, and soil freezing (Lawrence and Slater, 2005).
The NCAR-based Community Climate System Model (CCSM) utilized the projected high
and low greenhouse-gas emissions for the twenty-fi rst century as constructed by the IPCC.
The simulations suggest that half of the area covered by the upper 3-4 m of permafrost
could thaw by 2050 and as much as 90% by 2100. This would dramatically change the
polar ecosystems. In northern Canada, Alaska, Greenland, and northern Scandinavia,
there would be damage to buildings, roads and other structures, and mining and other
activities would be severely affected. For example, certain winter (ice) roads would no
longer be possible. The impact upon buildings and infrastructure in northern Russia
would be even more catastrophic (see pp. 387-388). A general and qualitative assessment
of the predicted impacts due to a 3 °C warming of permafrost is provided in Table 15.1.
Table 15.1.
Qualitative assessment of projected impacts that might result from a 3 °C warming
of permafrost.
FEATURE/PARAMETER
CONTINUOUS
DISCONTINUOUS
PERMAFROST
PERMAFROST
TERRAIN
TERRAIN
None
Low
Moderate
Severe
Low
Moderate
Severe
Thaw Lakes
X
X
Coastal Processes
X
X
Eolian Activity
X
?
<−
X
Veget at ion
X
−>
X
X
−>
X
Active-Layer Thickness
X
X
Permafrost Thawing
X
X
(table and base)
Thaw Settlement
X
X
Slope Instability
X
X
Erosion
X
X
Solifl uction
X
X
Engineering Impacts
X
X
Source: Weller and Lange (1999).
