Permafrost

Assessment
The main regularities of permafrost extent in the Southern Siberia and
in Mongolia
(In connection with small-scale mapping of permafrost in the Central Asia)
G.F.Gravis,L.A.Konchenko *
168
(Institute of Earth Cryosphere, Russian Academy of Sciences, Moscow, Russia)
Abstract: In the Asian region, on N.A.Marinov (1968), there are two largest permafrost massifs:
Northern-Asian and Southern-Asian. The southern part of the Northern-Asian massif and the
Southern-Asian massif were formed and exist only due to severe climatic conditions of
mountains, highlands and plateaus.
The mountain relief causes complex permafrost distribution. There are no enough
boreholes and excavations for exact mapping of mountain permafrost. Therefore with a view of
small-scale geocryological mapping with scope of vast territories exclusively great value get the
general regularities of permafrost distribution. These regularities allow to interpolate and
extrapolate of individual geocryological data on mountain territories correctly. Revealing of
these regularities is carried out with the help direct and indirect cryoindicators. The direct
cryoindicators are carried out on the cryogenic forms studying of a relief which can be formed
only at permafrost presence: pingos, cementry mounds and the some kinds (but not all) of
solifluction forms. The indirect cryoindication is carried out by landscape methods.
The analysis of results Russian, Russian-Mongolian and Mongolian geocryological
researches shows, that within the limits of mountains of the Southern Siberia and Mongolia
regularities of permafrost distribution are identical. It has allowed to compare geocryological
maps of Russia and Mongolia by compiling Circum-Arctic Map of Permafrost and Ground Ice
Conditions (1997).
There are three directions of increase of permafrost extent:
• in a direction from the south on the north;
• in a direction from below upwards;
• in a direction from the west on the east (separately for each mountain massifs).
In a direction on the south the massif of continuous permafrost separates up to islands and
isolated patches. In a direction from below upwards permafrost extent grows - first of all in the
north of region, and then in the south. In both cases the predominating role belongs to thermal
factors. In a direction from the west on the east of mountain massifs the extent of permafrost is
depending on an exposition of slopes, on changes atmospheric precipitation caused by the
western air transfer. On the western slopes of mountains because of a high snow cover
permafrost distribution is less than on east ones (Altai, Saiany, Khangai, Khentei).
With a view of engineering practice on a small-scale map of the Central Asia it is expedient to
show two types of territories:
• the territories where the permafrost is absent because of a high snow cover (removal or
compression of a snow causes aggradation of permafrost);