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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 2
The Cryosphere, 12, 595-608, 2018
https://doi.org/10.5194/tc-12-595-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
The Cryosphere, 12, 595-608, 2018
https://doi.org/10.5194/tc-12-595-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 21 Feb 2018

Research article | 21 Feb 2018

Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai–Tibet Plateau

Youhua Ran1,2, Xin Li1,2,3, and Guodong Cheng1,4 Youhua Ran et al.
  • 1Key Laboratory of Remote Sensing of Gansu Province, Heihe Remote Sensing Experimental Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China
  • 3CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China
  • 4Institute of Urban Studies, Shanghai Normal University, Shanghai 200234, China

Abstract. Air temperature increases thermally degrade permafrost, which has widespread impacts on engineering design, resource development, and environmental protection in cold regions. This study evaluates the potential thermal degradation of permafrost over the Qinghai–Tibet Plateau (QTP) from the 1960s to the 2000s using estimated decadal mean annual air temperatures (MAATs) by integrating remote-sensing-based estimates of mean annual land surface temperatures (MASTs), leaf area index (LAI) and fractional snow cover values, and decadal mean MAAT date from 152 weather stations with a geographically weighted regression (GWR). The results reflect a continuous rise of approximately 0.04°Ca−1 in the decadal mean MAAT values over the past half century. A thermal-condition classification matrix is used to convert modelled MAATs to permafrost thermal type. Results show that the climate warming has led to a thermal degradation of permafrost in the past half century. The total area of thermally degraded permafrost is approximately 153.76×104km2, which corresponds to 88% of the permafrost area in the 1960s. The thermal condition of 75.2% of the very cold permafrost, 89.6% of the cold permafrost, 90.3% of the cool permafrost, 92.3% of the warm permafrost, and 32.8% of the very warm permafrost has been degraded to lower levels of thermal condition. Approximately 49.4% of the very warm permafrost and 96% of the likely thawing permafrost has degraded to seasonally frozen ground. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88, 97, 155, 185, 161, and 250m, respectively. The degradation mainly occurred from the 1960s to the 1970s and from the 1990s to the 2000s. This degradation may lead to increased risks to infrastructure, reductions in ecosystem resilience, increased flood risks, and positive climate feedback effects. It therefore affects the well-being of millions of people and sustainable development at the Third Pole.

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Approximately 88 % of the permafrost area in the 1960s has been thermally degraded in the past half century over the Qinghai–Tibetan Plateau. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88 m, 97 m, 155 m, 185 m, 161 m, and 250 m, respectively. This degradation may lead to increases in risks to infrastructure, flood, reductions in ecosystem resilience, and positive climate feedback.
Approximately 88 % of the permafrost area in the 1960s has been thermally degraded in the past...
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