Investigation of changes in thermokarst lake distribution in West Siberiaby multitemporal satellite images

Investigations of changes in thermokarst lake by multitemporal satellite images were created by researchers of Russia, Canada and the USA. Results of these investigations in West Siberia are different. Scientists from the Tomsk University and American researches revealed increase of lake areas in the Northern geocryological zone and decrease of them in the Southern geocryological zone. They explain this fact by the influence of the global warming. But the investigators from the Moscow State University revealed that the lake areas are practically stable in both geocryological zones, except the small decrease because of erosive activity of rivers. Consequently we have carried out detailed investigations using different methods to specify type of changes of the thermokarst lakes areas. Investigations were based on comparison of space images, mainly from Landsat satellites, taken in 1970ies - the beginning of 1980ies and in 2000ies, with interval of 20-30 years. The analysis of multitemporal images was made for 3 test sites (in the upper reaches of the river Nadym, on the Gydansky and Yamal peninsulas). These test sites partially overlap test sites that were analyzed by scientists from the Tomsk University. Our investigation confirmed relative stability of thermokarst lakes and small local decrease of thermokarst lake areas in both geocryological zones caused by erosive activity of rivers. The investigation showed necessity of precipitation registration in the period before the date of observation. Precipitations may be the source of mistakes. The other cause of divergence in results is the differences in methods. Scientists from the Tomsk University analyze only large lakes (more than 20 hectares), but our investigations include analyzes of all the lakes by the use of mapping the dynamics of lakes. We consider that our method is more reliable.

thermokarst lakes, multitemporal satellite images