National Institute of Polar Research, 1-9-10 Kaga, Itabashi-ku, Tokyo 173-8515
Recent studies have described mountain permafrost degradation due to global warming in many mountain regions, such as European mountains, the Tibetan Plateau, the Tien Shan and mountainous areas of Mongolia. In this chapter we describe the recent mountain permafrost degradation in the Nepal Himalayas and the Russia Altai Mountains. The Nepal Himalayas is one of the largest mountainous areas of the world. In 1973, the permafrost lower limit was estimated to be 5200-5300 m above sea level (ASL) on southern-aspect slopes in the Khumbu Himal, the eastern part of the Nepal Himalayas. Using ground-temperature measurements, the mountain permafrost lower limit on slopes with the same aspect was estimated in 2004. The results indicate that the permafrost lower limit was 5400-5500 m ASL in 2004. The permafrost lower limit was estimated to be 5400 to 5500 m on slopes with a southern aspect in the Khumbu Himal in 1991 using seismic reflection soundings. Thus, it is possible that the permafrost lower limit has risen 100-300 m between 1973 and 1991, followed by a stable limit of 5400 to 5500 m over the last decade. The Russia Altai Mountains is located on the southern fringe of the Siberia Plain. The altitudinal range of sporadic/patchy permafrost zone and that of discontinuous/continuous permafrost zone are 1800-2000 m ASL and above 2000 m ASL, respectively. The mean annual air temperature at Russian meteorological stations in Russian Altai exhibited remarkable warming trends. We observed the phenomena relating to permafrost degradation, such as landslide influenced by antecedent permafrost degradation, and rapid degradation of pingos around the lower limit of discontinuous/continuous permafrost zone.
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