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The second is an alpine location in low latitude where diurnal temperature variations
dominate over weak seasonal infl uences. Numerous shallow freeze-thaw cycles occur
throughout the year and precipitation may vary from near-arid to humid, depending upon
location. These climatic conditions exist near the summits of the various mountain ranges
in South America, East Africa, and near the summit of Mauna Loa, Hawaii. Clearly, they
are not extensive in area.
3.2.6. Antarctica: A Special Case
The climate experienced by the ice-free areas of Antarctica fi nds no easy place in any
climatic classifi cation. This is because Antarctica has a range of climates that refl ect the
vast size and unique location of the continent. The mildest are those experienced by the
Antarctic Peninsula that extends northwards into the South Atlantic Ocean. The harsh-
est are those experienced by the ice-free summits of the Trans-Antarctic Mountains and
the other small nunataks that protrude through the vast Antarctic ice sheet. In between
in character are a number of relatively small ice-free locations that surround the conti-
nent. These are close to open water during 1-3 months of the year but may be over
100-200 km away from the edge of the maximum expansion of the surrounding sea ice
in winter.
The ice-free areas in southern and northern Victoria Land constitute a special case.
They result from strong katabatic winds that promote sublimation to such an extent that
perennial snow and ice is unable to form. These environments are best described simply
in terms of their air temperature and wind characteristics (see Table 3.1). For example,
Table 10.7 presents data from several automatic weather stations maintained by the Italian
Antarctic Program (PNRA) within a 50 km radius of their coastal station at Terra Nova
Bay, northern Victoria Land. The mean annual temperature ranges between
15 °C at the
coast to
24 °C inland. Only the coastal station records average air temperatures that rise
above
5 °C. Equally important is the exceptional strength and duration of the wind. For
example, the station located on Inexpressible Island records near-continuous wind fl owing
outwards from the Priestley Glacier at speeds in excess of 50 km/hour for over 51% of the
time. Clearly, the ice-free areas that surround the Antarctic continent are some of the
coldest, windiest, and driest areas on Earth.
3.3. GROUND CLIMATES
Air temperatures are a useful way of characterizing periglacial climates. However, tem-
perature at the ground surface and the immediate near-surface are probably more relevant
when considering cold-climate weathering processes and permafrost formation.
Typically, there are signifi cant differences between air and ground temperatures. These
refl ect either the effects of vegetation or the ameliorating effect of snow cover (Burn and
Smith, 1988a; Goodrich, 1982; Mackay and MacKay, 1974). However, the situation is
complex because wind also infl uences snow cover and its redistribution. The latter can
protect the ground from the negative effects of wind or, conversely, can promote desicca-
tion and abrasion by wind-driven snow particles. These and other wind-induced effects
become especially important near the northern treeline (Scott et al., 1993) and in the
tundra regions. Water bodies are a further complication.
Some of these interactions can be illustrated by data that lists annual mean air, ground
(surface), and lake-bottom temperature at a number of sites in the Mackenzie Delta region
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