Permafrost

soundings, borehole temperature measurements and field analysis for ice content and density of
more than 150 samplings along the Sharga valley transect in the southwest of the region (Gravis
and Sharkhuu, 1968), (3) observations for distribution of cryogenic phenomena in the
northeastern part of the region (Sharkhuu) and (4) shallow borehole drillings in the central part
of the region (Sharkhuu, 1973). The results of the above studies are published in a number of
scientific papers and used for compiling geocryological map of Mongolia (Gravis, 1974., and
Sharkhuu, 1976)
The objective of the investigations (1983-1987) in the second stage was to study
temperature regime of mountain permafrost in the central part of the region. According to the
investigations, Sharkhuu (1983-1987) made ground temperature measurements in more than
100 deep boreholes, located in the Burenkhan and Hovsgol phosphorite deposit areas. Using the
result of measurements, we estimated values of changes in mean annual temperatures of
mountain permafrost depending on altitudes, slope aspect, geological and landscape conditions.
Based on the estimation, permafrost maps of the Hovsgol deposit areas (1:100000) and Hovsgol
Province (1:1000000) (by Sharkhuu) are compiled in 1989 for specific purposes.
The third stage of the studies, since 1996, is related to long-term monitoring of permafrost
in the region. The monitoring is carried out by Sharkhuu within the framework of the
international CALM and GTN-P projects in Mongolia. Main parameters of the monitoring are
values of changes in active layer thickness and mean annual permafrost temperatures, which are
estimated by measuring or recording ground temperatures in the monitoring 5-15 m and deeper
boreholes. At present, there are 19 boreholes of both CALM and GTN-P in the region. Some of
the boreholes are redrilled in last years in the same points where old closed ones were
investigated very well 15-35 years ago. In addition, dynamics of some cryogenic phenomena
are monitored at the certain sites. Initial results of the monitoring show that permafrost in the
Hovsgol Mountain Region is degrading more intensively under influence of recent climate
warming than in the Khangai and Khentei Mountain Regions. Meanwhile, permafrost
degradation during last 15-20 years was more intensive than during previous 15-20 years
(1970-1990). Average rates of increase in active layer thickness and mean annual permafrost
temperatures in the region are 3-30 cm and 0.2-0.4 o C, respectively. Relatively deep thermokarst
lake and hollow, and active thermoerosion process are characteristic of Darhad depression.
Permafrost studies in the fourth stage, starting since 2002 are conducted in six valleys
along the northeastern shore of Lake Hovsgol. The new studies are carried out within the
framework of international project “Impacts of nomadic pasture use and climate change on
watershed ecosystems, biodiversity and permafrost of the boreal forest and steppe of northern
Mongolia” (Goulden, 2002). The project is funded by a five-year grant from the Global
Environmental Facility to the Mongolian Academy of Sciences, implemented by the World
Bank. The main purpose of the studies are (1) to study permafrost conditions and (2) to monitor
recent degradation of permafrost under influence of climate warming and human activities,
such as nomadic pasture, forest cutting and fire in the project area. During last four years
Mongolian and Norwegian permafrost researchers carried out the following field investigations:
19 borehole drilling with depth of 5 to 10 m, borehole temperature measurements by movable
thermistor strings, leveling measurements of frost heaving and thaw settlement at 6 sites
(Sharkhuu, 2002-2005), resistivity tomography soundings at 18 sites (Etzelmuller, 2002 and
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