Permafrost

studies (Natsagdorj et al. 2000), the mean annual air temperature in Mongolia has increased by
1.56°C during the last 60 years.
Monitoring of permafrost in Mongolia is started since 1996. Main purpose of the
permafrost monitoring is to estimate values of recent changes in permafrost under influence of
climate warming and human activities, such as land use in Mongolia. The monitoring is carried
out within the framework of the Circumpolar Active Layer Monitoring (CALM) and Global
Terrestrial Network for Permafrost (GTN-P) programs. In addition, some cryogenic processes
and phenomena are monitored at different monitoring sites.
The main criteria of permafrost monitoring are active layer depth and mean annual
permafrost temperature at the level of the zero annual amplitude. Long-term CALM and GTN-P
programs are based on ground temperature measurements in shallow to deep boreholes. Each
borehole for monitoring is installed by certain instrumentation in order to protect air convection
in them. Temperature measurements in the boreholes are made using the same thermistors at the
corresponding depths, and carried out on the same dates of any year. In addition, temperature
data loggers and thaw tubes are installed in some of the boreholes. Monitoring of frost heaving,
thermokarst and icing is based on leveling measurements.
At present, we have 14 sites of permafrost monitoring in Mongolia. There are five
(Baganuur, Nalaikh, Argalant, Terelj and Gurvanturuu) sites in Khentei, two (Terkh and Chuluut)
sites in Khangai, six (Sharga, Burenkhan, Hatgal, Ardag, Hovsgol Project and Darhad) sites in
Hovsgol, and Tsengel site in Altai mountain regions. Each site has one or several monitoring
boreholes with depth of 5 to 15 m. A depth of six boreholes reaches 50-80 m. At present, there
are 37 both CALM and GTN-P active boreholes in Mongolia. Most of 5-15 m deep boreholes
are redrilled during last 10 years in the points where old closed deep ones were investigated
well (in a detail) 15-35 years ago. Therefore, the monitoring of permafrost in Mongolia is
long-term.
The initial results of permafrost monitoring show that permafrost under influence of recent
climate warming and human activities in Mongolia is degrading with different rates depending
on regional and local character of changes in climate and natural conditions. The rates of
increase in active layer depth and mean annual permafrost temperatures vary 3-30 cm and
0.1-0.4 o C, respectively. A rate of permafrost degradation in bedrock is more than that in
unsolidated sediments, in ice-poor substrates more than in ice-rich ones, on south-facing slopes
higher than on north-facing ones, and at sites with human activities more than at those without
them. A temperature gradient of permafrost is increasing with depth. For example, permafrost
temperature gradient in Darhad depression was 0.025 o C/m at 20-50 m depth and 0.038 o C/m at
50-80 m depth. In generally, permafrost degradation during last 15-20 years was more
intensively than during previous 15-20 years (1970-1990s). Meanwhile, the permafrost in the
Hovsgol Mountain Region is degrading more intensively than that in the Khentei, Khangai
Mountain Regions.
Dynamics of thermokarst thermoerosion, frost heaving, solifluction, kurum and icing are
monitored at seven sites of the Hovsgol, Khangai and Khentei Regions. Especially, the
thermokarst and the thermoerosion are direct indicators of ancient and recent degradation of
permafrost under climate warming. By visual observation during last 30 years, a rate of settling
due to thermokarst processes (lake and sink) at Chuluut (in Khangai) and Nalaikh (in Khentei)
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