Permafrost

part of soil profile in pine forest following: 4 (6) - 0 cm – over surface cover from a foxberry,
0-2 (3) cm – litter from weakly decomposed plant remains and clay sandy and sandy horizons
are below.
The summer of 2002 is characterized as dry and warm. During the period from May to
October, precipitation was only 90.2 mm (out of a mean of 174.9 mm for the same period), the
average temperature of the season was equal to 12.3 degC. (with at long-term mean value of
12.2 degC. The summer season of 2003 was close to the mean. During the period from May to
October, precipitation was 153 mm, the season was warmer than the mean and averaged 13
degC. At almost identical conditions of warming and moisture the compared sites appreciably
differed on depth of seasonal thawing.
The maximum depth of seasonal thawing of the grassland soil on site 1 in 2002 reached
3m, on site 2 – 2.1 m. For the summer of 2003, depth of seasonal thawing of grassland soils
reached, 2.4 and 1.0 meters respectively. The depth of active layer of forest soils at 2002
summer reached on site 3 – 1.4 m, on site 4 – 2.1 m, corresponding parameters for 2003 were
equal to 1.6 and 2,3 m. Such difference in soil thawing depth is caused by structure of the soil
profile. It is known, that the soil horizons enriched with organic substance, possess increased
moisture capacity and low heat conductivity. Due to these properties in grassland soil on site 2
and forest soil of site 4, depending on weather conditions of summer season, the depth of
seasonal soil thawing reached only 50-70 % those of on sites 1 and 3.
Thus, the morphological structure of soils plays an essential role on seasonal soil thawing
depth in cryolithozone.
Key words: Central Yakutia, cryolithozone, soil structure, thawing depth, umus-accumulative
horizon, sod humus horizon
82
Rock Temperature Regimes in Northern Norway and on Svalbard:
Implications for Cryogenic Weathering
Angélique Prick
(International Permafrost Association Secretariat (IPA) / University Centre in Svalbard (UNIS),
P.O. Box 156, N-9171 Longyearbyen, Norway)
Abstract: The study of cryogenic rock weathering features and the monitoring of rock
temperature have been carried out in Longyearbyen, Svalbard (78º N, 15º E) since 2001 and
along a West-East gradient across the Troms county, Norway (69-70° N, 16-21° E) since 2004.
Temperatures are monitored in blocks and in rockwalls at depths of 40 cm, 10 cm, 1 cm and at
the rock surface.
On Svalbard, the monitored sandstone rockwall is experiencing considerable temperature
fluctuations, even during the polar winter. The freezing of the rockwall in the autumn and
particularly its thawing in the spring bring along several freeze / thaw cycles at the rock surface.
40 centimeters into the rockwall, the rock freezes once in the autumn and remains frozen until
May. On Svalbard, conditions favourable to cryogenic weathering (i.e. freezing of the rock
when its moisture content is high) are met only rarely. But when these conditions are met, frost
action can be very aggressive, because of the high rock moisture content, the quick cooling or