InterCarto. InterGIS (Jan 2017)
ASSESSMENT OF THE DYNAMICS OF THERMOKARST LAKES BASED ON THEIR MORPHOLOGICAL AFFILIATION
Abstract
We have proposed an approach to estimating the areal dynamics of thermokarst lakes. It takes into account the role of the main factors in the development of the lake thermokarst, one of the most common processes in the accumulative plains of Russian permafrost zone. One of the factors is the morphological structure which determines the drainability of the earth’s surface; it is genetically related to manifestation of the lake thermokarst.The research has involved the archival aerial images, Landsat space images, digital elevation model according to ASTER data, topographic, geological and tectonic maps and charts.In the morphostructural zoning, an area ratio of the residual edoma to alases was the most important criterion. The zoning was controlled and supplemented by the analysis of a longitudinal grade of similar rivers, plan view of the hydrographic network pattern, and coefficient of river sinuosity. The analysis of the digital elevation model (DEM), which showed differentiation of surface elevations and down-cutting of rivers and alases, played an important role.The local morphostructures with an area of thousands – the first tens of thousands of square kilometers, representing the alas plains with scattered fragments of the edoma, are identified as negative morphostructures. The territories of Ice Complex with the limited area of alases (less than 50 %) form positive morphostructures.We have measured the area of thermokarst lakes using multi-temporal remote sensing data for the Shirokostan Peninsula and adjacent territory, selected as a key site. No significant change for the lakes has been registered within the positive morphological structure. The negative morphological structure is characterized by the following: 1) the number of lakes and their area exceed those in the positive morphostructure; 2) the number of lakes that reduced their area is greater than the increased ones due to the natural migration of the river network and its draining influence; 3) the total increase of the area of lakes predominates over the decrease, which is most typical for large lakes. This process occurs due to thermal abrasion of the shores of the low-lying coastal territory, which is composed of rocks with polygonal ice wedges.
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