Conclusion

The permafrost lower limit on slopes with a southern aspect in the Khumbu Himal was estimated as 5200 to 5300 m in 1973 and was determined 5500 m in 2004 based on the ground temperature data. In 1991 the permafrost lower limit on slopes with a southern aspect was estimated as 5400-5500 m 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 permafrost lower limit rose 40-80 m at the Tibetan Plateau as estimated by an increase in mean annual air temperature of approximately 0.2 to 0.4°C from the 1970s to the 1990s (Wang et al., 2000). The larger rise in the mountain permafrost lower limit in the Khumbu Himal than that in the Tibetan Plateau suggests that climate warming in the Khumbu Himal has been more severe than that in the Tibetan Plateau.

The sporadic/patchy permafrost zones extend from 1800-2000 m ASL and the widespread discontinuous/continuous permafrost zones are above 2000 m ASL in the Russian Altai Mountains. The MAATs at Russian meteorological stations in the Russian Altai Mountains exhibited significant warming trends for 1965-2000. We observed two notable phenomena related to permafrost degradation in the Russian Altai Mountains. First, slope instability caused by permafrost degradation induced a large landslide. Second, we noted remarkable pingo degradations. These phenomena suggest a rapidly rising lower limit of permafrost in the Russian Altai Mountains.

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