Geology Reference
In-Depth Information
Table 3.6.
Simulated climate change in the Fennoscandia region due to a doubling of the
atmospheric CO
2
content, according to a scenario derived from the GISS model.
Climate parameter
Climate change
Magnitude
Increase (
+
)
or decrease (
−
)
Mean annual temperature
+
4-5 °C
Mean winter temperature
+
5-6 °C
Mean summer temperature
+
2-3.5 °C
Annual temperature amplitude
+
2-4 °C
Length growing season (daily mean temp.
≥
5 °C)
+
70-150 days
Effective temperature sum (threshold
≥
5 °C)
+
500-1000 degrees
Length thermal winter (daily mean temp.
≤
0 °C)
−
2-4 months
Length thermal summer (daily mean temp.
≥
10 °C)
+
2-3 months
Number heating degree-days (daily mean temp.
≤
17 °C)
−
30-40%
Mean annual precipitation
+
150-300 mm
Precipitation excess
+
10 -50%
Source: Boer et al., (1990).
≥
5 °C) would increase by 70-150 days, and precipitation would increase by 150-300 mm.
Clearly, if the changes predicted for Fennoscandia are typical of those predicted for other
high-latitude regions, then the extent of periglacial climates, and by extension the perigla-
cial domain, will change radically. Even in low latitudes, the effects of global warming
will be important. For example, a recent rise in the mean annual ground temperature on
the Tibet plateau between 1962 and 1989 suggests that permafrost may disappear from
the Tibet plateau in approximately 150 years.
Many periglacial environments have high negative radiation budgets. Changes in their
budgets will prompt major changes in atmospheric and oceanic circulation. For example,
the melt of sea ice and ice shelves promotes the formation of cold bottom waters that drain
equator-ward and infl uence oceanic circulation patterns. The polar seas are also large
sinks for CO
2
and play an important role in the exchange of CO
2
between ocean and
atmosphere.
Positive feedback mechanisms will accelerate global warming in cold regions. For
example, the melt of sea ice and seasonal snow cover will reduce albedo and increase solar
radiation inputs at the ground surface. Large terrestrial CO
2
and CH
4
(methane) reser-
voirs will be released as temperatures rise and permafrost thaws in boreal forest and
tundra regions.
In summary, the periglacial domain is susceptible to signifi cant change, both in char-
acter and extent, if present and predicted global warming trends continue. The cryosphere,
of which the periglacial domain is a major component, will play an important role. The
implications of climate warming are discussed further in Chapter 15.
ADVANCED READING
IPCC (Intergovernmental Panel on Climate Change) (2001). Third Assessment Report. WGI.
Climate
Change
2001:
The
Scientifi c
Basis
(Houghton, J. T., et al., eds.), 881 pp., and WGII,
Climate
Change
2001:
Impacts,
Adaptations
and
Vulnerability
(McCarthy, J. J., et al., eds.), 1032
pp., Cambridge University Press, Cambridge.
