GENERAL WETNESS AND FLUCTUATIONS IN THE ALAS LAKE LEVEL IN CENTRAL YAKUTIA
Bosikov, Nickolai (1)
(1) Melnikov Permafrost Institute, Russian Academy of Sciences
Central Yakutia alasses are the unique permafrost landscapes with peculiar soils and meadow vegetation defined as a dynamic system whose initiation, growth and development are closely related to the climate dynamics.
Alas lakes have no surface outflow and that's why they enlarge and shrink, depending on precipitation and evaporation variability. We investigated a series of lacustrine deposits in Central Yakutia for the purpose of reconstruction of fluctuations in the alas lake level. Historical and interview data show that in the mid-twentieth century the alas areas were dry. In the latter half of the nineteenth and the early twentieth centuries lakes formed in most alasses. The cuts obtained from the trees which grew on the alas bottoms in the dry period show that drying-out of the alasses (a dry period) lasted for 100-120 years.
On the basis of investigations on the rise of the alas lake level we conclude that the rise of the alas lake level in spring occurs when the following meteorological conditions coincide: a) heavy rains in autumn before freezing of the seasonally thawed layer; b) the depth of winter snow cover close to or greater than the mean long-term norm; c) short and warm spring. For example, the sharp rise of the alas lake level in 1967 occurred under such conditions.
The repeated drying and ponding of alas depressions for the last three millennia have been found from the study of bottom deposits in the alas lakes. A plot of general wetness variability in Central Yakutia for a long period has been compiled through investigations of bottom deposits from alas lakes, including radiocarbon dating.
The revealed fluctuations in the alas lake level and analysis of atmospheric precipitation suggest the dependence of alas water levels on general wetness which in turn depends on the cyclonic movement from west to east and from Pribaikalje or Mongolia to north-east.
Submittal Information
Name :
Date :
Bosikov, Nickolai
30-May-01-19:26:39
Organization :
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Melnikov Permafrost Institute, Russian Academy of Sciences
