Permafrost

• the territories where the permafrost is absent because of low ground humidity
(permafrost forms after inevitable increasing of ground humidity by engineering of such sites;
this process is accompanied by formation of icings and pingos).
Key words: permafrost extent, cryoindicators, small-scale mapping of permafrost.
Local-level processes associated with progressive permafrost thaw as
examplified by data from a CALM grid
Galina Mazhitova and Dmitry Kaverin
(Komi Science Centre, Russian Academy of Sciences, Syktyvkar, Russia)
Abstract: Active layer depths in the permafrost area of the European Russian North have been
demonstrating clear increasing trend during the recent three decade covered with geological and
CALM (Circumpolar Active Layer Monitoring) records (Oberman & Mazhitova, 2001;
Mazhitova et al., 2004). In a non-linear way, the trend corresponds to climate dynamics during
the same period, first of all, to the increasing trend in thaw degree days in air.
Local-level processes related to the progressive permafrost thaw are often
landscape-specific and not yet well studied. CALM design allows for statistical studies on
these processes with further upscaling to the regional level. The paper discusses such studies
examplified with data from the 100x100 m Ayach-Yakha CALM grid located in the
discontinuous permafrost zone of the European Russian North (67 0 35.4'N; 64 0 09.9'E). The
deposit is silty loam, vegetation is dwarf shrub/moss tundra, and frost boils occupy 3% of the
site area.
General Linear Model analyses were used to find landscape predictors of thaw depth and
to assess their relative input to thaw variability. Examined factors were the conventionally
defined “macro-“ and “meso-“ topography (within-grid ranges of 5 m and 1.1 m, respectively),
volumetric soil water content (14-73%), snow depth (0-70 cm), vegetation (dwarf shrub/moss
class and tall shrub class) and soil organic layer thickness (5-23 cm). In different years the
examined factors explained in total 5-35% of the end-of-season thaw depth variability. Effect of
organic layer was most sensitive to thaw depth showing logarithmical trend (R 2 =0.18).
Long-term increase in thaw depth thickness in permafrost regions causes surface
subsidence, which is one of potentially hazardous consequences of climate warming. In the
termokarst-prone terrain types, i.e. those with high ice content in permafrost, subsidence
combined with other processes can lead to catastrophic changes of surface topography. Terrains
with smaller ice contents in the ground still experience subsidence. Subsidence measurements
were conducted annually in 1999-2005 at the end of warm season. Site-averaged retreat of
permafrost table totaled 33 cm during this period. Accompanied with site-averaged subsidence
of 17 cm, it resulted in a 16 cm increase in active layer depth. Subsidence (or heave at few grid
nodes) values were well correlated with node-specific amounts of downward or upward shift of
the permafrost table (R 2 =0.76). Normalized subsidence index (a ratio of subsidence to
permafrost retreat) approximating the ice content in the ground averaged 0.52 for the
observation period. It was found that the differential subsidence changed the site surface
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