TXT-tool 1.086-1.1 Distribution of island-like permafrost in the lesser khingan mountains of northeast china using landsat7 etm+ imagery

Abstract

In northeast China, at high-latitudes permafrost shows remarkable degradation in response to global changes, evidenced by the northward retreat of the southern boundary, and by shrinkage and fragmentation of the distribution of the permafrost. In these areas, the difficulty of establishing the spatial distribution of permafrost via conventional survey methods inhibits permafrost research, and has practical implications for activities such as highway engineering and construction. Permafrost thaw has serious implications and is associated with increased incidence of landslides and subsidence of many highway roadbeds constructed in the northern area of the Heilongjiang Province, China. To study the regional distribution of island-like permafrost, we selected the Bei’an to Heihe highway, from K153 to K183. We use three Landsat7 ETM+ images obtained in March, May, and September 2009. The land surface temperature (LST) in the research area was retrieved using the radiation transfer equation method. We thereby derived a surface temperature map corresponding to the image acquisition times. The reliability of the surface temperature map was verified by comparison with weather station data. According to the distribution characteristics of permafrost fragments in the study area, LST was selected as the main energy index of permafrost distribution. Permafrost distribution criteria were developed to obtain a permafrost distribution map of the study area in 2009, assisted by empirical interpretation. The estimated permafrost distribution shows a good agreement with field survey data. The findings can contribute to surveying, route selection, and maintenance of highways.