Thermal Characteristics

Probably the most striking thermal characteristics of Arctic soils are the low soil temperatures, the steep vertical temperature gradient, and the perennially frozen nature of a portion of the subsoil. Although soil temperatures are directly related to

Fig. 1.3 Cryoturbated microfabric showing oriented sand grains
Fig. 1.4 Cryoturbated microfabric showing lenticular or platy structure

air temperature (Fig. 1.5), factors such as vegetation cover, soil moisture, thickness of snow cover, and underlying permafrost have a modifying effect. Since the active layer has very little buffering capacity, however, soil temperatures rapidly reflect fluctuating air temperatures, especially when they are cooling (Tarnocai 1980).

Relationships between air temperature and soil temperatures at depths of 50 and 100 cm at two latitudes are shown in the graphs in Fig. 1.5. The Overlord site (Fig. 1.5a)

Jan March May July Sept Nov Month

10 0 10

10 0 10

Jan March May July Sept Nov

Month

Jan March May July Sept Nov

Month b

-Air

-100

Fig. 1.5 Mean monthly soil (50 and 100 cm depths) and air temperatures measured in 1999 on southern Baffin Island (a) and northern Ellesmere Island (b) in the Canadian Arctic a on Baffin Island in the southern part of the Arctic (Lat. 66° 23' 30" N; Long. 65° 29' 20" W) has temperatures above zero at the 0-100 cm depth during the summer months. At the Lake Hazen site (Fig. 1.5b) on Ellesmere Island in the High Arctic (Lat. 81° 49' 15" N; Long. 71° 33' 17" W), however, only the surface 0-45 cm of the soil thaws during the summer months; below this depth, the soil remains frozen throughout the year.

As a result of the very thin and compacted snow cover in much of the Arctic region, the subsoil cools rapidly as the air temperatures drops, leading to a very small, or negligible, thermal gradient in the soil, especially in the High Arctic (Tarnocai 1980).

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