Geoscience Reference
In-Depth Information
example from a calving event prior to the recent breakup is the ice island T-3 (also
known as Fletcher's Ice Island), which was used as a platform for meteorological
surveys and ocean research between 1952 and 1978.
2.2.2
Land Cover
The Arctic lands are commonly subdivided into the High Arctic and the Low Arctic
based on broad climatic, geographical, and biological grounds (Bliss,
1997
), but
many ecologists recognize five subzones (Walker et al.,
2002
). As a general state-
ment, the High Arctic is characterized by more severe environmental conditions
than the Low Arctic, reflected in the type and distribution of vegetation.
Land in the High Arctic is generally characterized by tundra, a Finnish term for
treeless upland. More generally, tundra refers to the treeless regions north of the
Arctic tree line. The most extreme High Arctic tundra landscape falls under the
category of polar desert, which implies both cold and a lack of moisture. Good
examples are provided by the Canadian Arctic Archipelago and Peary Land in
northeast Greenland. The concept of polar desert was introduced by the German
geographer S. Passarge (
1920
). Subsequently, the term has been applied in a geo-
botanical context by V. Alexandrova (
1970
).
Figure 2.14
shows the extent of polar
desert as interpreted by R. Charlier (
1969
). E. Korotkevich (
1972
) includes ice caps
and the Greenland Ice Sheet in the polar desert category.
Field studies of polar desert sites on 10 islands in the Canadian Arctic Archipelago
showed only 2-3 percent plant cover (Bliss,
1997
). The brief summers are rela-
tively warm, but scant moisture permits only a few cushion-form plants, mosses,
and lichens to grow in niches with favorable microclimates, particularly at sites
where snow banks provide melt water. In these favored areas, which occupy about
3-5 percent of the landscape, about 25-35 percent of the surface is typically vege-
tated. Vegetation is suppressed under semi-permanent snow banks. As discussed by
J. Ives (
1962
), for north-central Baffin Island, it is possible that the limited cover of
lichens and vascular plants is attributable to the widespread presence of snow banks
during the Little Ice Age (150-400 years ago).
Much of the polar and sub-polar desert surface is covered with fell fields (felsen-
meer), comprising gravel and angular blocks derived from freeze-thaw splitting of
the bedrock. As the first author can attest, such fell fields should be climbed only
with extreme caution. Stones and fine sediments are often organized as patterned
ground. This may consist of stone circles and ice-wedge polygons up to a few meters
across, or stone stripes on sloping surfaces (French,
1996
).
As for less extreme forms of tundra, in the North American Arctic, L.C. Bliss
(
1997
) distinguishes wet meadow (graminoid-moss) tundra comprised of dwarf-
shrub heaths and polar semi-deserts of cushion plants, cryptograms, and herbs. In
northern Russia, the so-called typical tundra (Chernov and Matveyeva,
1997
) is
predominantly moss and lichen covered (polar semi-desert according to Bliss), with
sedges and dwarf shrubs, and dry heaths. The vertical structure is about 20 cm in
height.
