Geology Reference
In-Depth Information
PERIGLACIAL CLIMATES
3.4. PERIGLACIAL CLIMATES AND THE CRYOSPHERE
The periglacial domain is part of the cryosphere. Terrestrial components include seasonal-
snow cover, mountain glaciers, ice sheets, perennially-frozen ground (permafrost), and
seasonally-frozen ground. The other important component of the cryosphere is Arctic sea
ice. Table 3.5 lists the extent of the terrestrial components of the cryosphere.
The cryosphere is particularly sensitive to global warming. Most global climate models
(GCMs) predict warming to be greatest is high latitudes. In particular, winter warming is
expected to exceed the global annual average. Projected changes in Arctic climates will
dramatically reduce sea-ice cover and signifi cantly degrade permafrost. In the Antarctic,
satellite sensors show changes in ice extent, including accelerated fl ow and thinning of
glaciers, and the break-up of parts of the Nansen and Ross Sea ice shelves (Shepherd
et al., 2001).
To appreciate the magnitude of some of these global changes, Table 3.6 lists what might
happen in Fennoscandia if there were a doubling of the CO
2
content in the atmosphere,
as modeled by the GCM developed by the Goddard Institute for Space Studies (GISS).
The model predicts mean winter temperatures will increase by 5-6 °C and mean annual
temperature will increase by 4-5 °C. Also, the growing season (daily mean temperature
Table 3. 5.
Relative extent of terrestrial areas of seasonal snow cover, ice, and permafrost.
Area (million km
2
)
Volume (million km
3
)
Land Ice:
Antarctica
13.9
30.1
Greenland
1.8
2.7
Small ice caps
0.35
0.2
Mountain glaciers
0.2
0.03
Major permafrost regions:
Percentage underlain by permafrost
Russia
16.84
50
Canada
9.38
50
China
9.38
22
Greenland
2.18
100
USA (Alaska)
1.52
82
World land area:
140.7
20-25
Northern Hemisphere
Con inuous
7.6
1
Discon inuous
17.3
1
2.33
1
Alpine permafrost
Volume (million km
3
)
Land ice and seasonal snow:
Area
Northern Hemisphere
Early February
46.3
0.002
Late August
8.7
Southern Hemisphere
Late July
0.85
Early May
0.07
1
Approximate.
Sources: Washburn (1979), Rott (1983).
