Permafrost

sites is estimated to be 3-10 cm per year. Maximum subsidence of up to 20-40 cm per year was
observed during the formation of incipient thermokarst pond at Chuluut site. During such
events, spring water discharges in thaw pond were 0.2-1.0 liter per second. In late August 2004,
one and half m thick active layer landslide on pingo ice table occurred on southeastern steep
slope of the degrading 5 m high pingo at Nalaikh thermokarst site. Small subsurface cavities on
the permafrost table are formed because of melting ice wedges in Darhad depression, Hovsgol
Region. Large cattle (yaks and horses) fell into deep (3 m) surface cavities and died there.
Although the vertical extent of some thermokarst depression and thermoerosional riverbanks in
Darhad depression reaches 15-25 m, the average is 3-7 m. In the 1970-s, Choiden Lake (in
Darhad degression), water body about 2 km in diameter disappeared due to thermoerosional
changes in the river channel leading to the lake. The lake depression dried gradually over the
last 15 years. In addition, a rate of thermo-erosion, based on the collapsing 6-8 m high Chuluut
River banks (composed of ice-rich lacustrine clays) is estimated to be in the range of 15 to 30
cm per year.
The recent degradation of permafrost under influence of climate warming leads to some
changes in natural and ecological balance. In particular, there are observed some processes of
desertification in steppe zone and deforestation in taiga zone of Mongolia.
Key words: active layer, permafrost temperature, thermokarst and thermoerosion
186
Mapping of Mountain Permafrost in Mongolia and Central Asia
N. Sharkhuu, Sh. Anarmaa
(Geo-Ecology Institute, Mongolian Academy of Sciences)
Abstract: According to the first recommendation of the International Symposium on Mountain
and Arid Land Permafrost (Ulaanbaatar, 2001), an international team experts from China,
Kazakhstan, Mongolia and Russia are required to prepare a uniform map of Central Asian
permafrost. Main tasks of the IPA working group on mapping and modeling of mountain
permafrost (ICOP, 2003) are to analyze the experience of permafrost map in the different
countries and to develop uniform legend for compiling Central Asian permafrost map. Different
principles and methods of permafrost classification and mapping in China, Kazakhstan,
Mongolia and Russia lead to some difficulties in compiling the uniform map. Moreover, initial
data for the map are very different in every mountain regions of Central Asia. The objectives of
this paper are to analyze present state of permafrost mapping in Mongolia and to put forward
for discussion the proposed draft of unified legend for compiling Central Asian permafrost map.
Present state of permafrost mapping in Mongolia. As a result of Joint Russian and
Mongolian geocryological expedition in 1967-1971, G. F. Gravis et al. compiled permafrost
map of Mongolia (1:1500000), which shows distribution of permafrost and cryogenic
phenomena. Based on latitudinal zones and altitudinal belts of permafrost distribution, the
permafrost zone of Mongolia is divided into geocryological areas of sporadic (80%) permafrost by
its extent. Subsequent mapping of permafrost in Mongolia has been carried out by N. Sharkhuu