Comparison of permafrost degradation under natural ground surfaces and embankments of the Qinghai-Tibet Highway

Permafrost under road embankments often degrades more seriously than that under natural ground surfaces due to the influences of both climate warming and road embankment. In a companion paper, we analyzed the states of permafrost degradation under road embankments in the five typical regions along the Qinghai Tibet Highway (Yu et al., 2013a). In this paper, the states of permafrost degradation under natural ground surfaces, near the road embankments, are analyzed based on up to 15 years of in-situ geothermal data, while that under road embankments are also further analyzed. On this basis, the states of permafrost degradation and related processes are compared between the natural ground surfaces and road embankments. Possible influences of climate warming and road embankment on permafrost degradation are discussed. The results show different characteristics of permafrost degradation under natural ground surfaces and road embankments. The contributions of climate warming and road embankment on the thermal regime of permafrost may vary during the process of permafrost degradation. (C) 2015 Elsevier B.V. All rights reserved.