Variation of temperature and permafrost along Qinghai—Tibet railway
CAI Hancheng1，2，LI Yong1，2，YANG Yongpeng1，2，TANG Caimei1，2，CHENG Libin3，LIU Kun1
(1. Northwest Research Institute Co.，Ltd.，China Railway Engineering Corporation，Lanzhou，Gansu 730000，China；
2. Qinghai Province Key Laboratory of Permafrost and Environmental Engineering，Golmud，Qinghai 816000，China；
3. The 93929 Troops of Chinese People?s Liberation Army，Lanzhou，Gansu 730000，China)
Abstract：The permafrost on the Qinghai—Tibet plateau(QTP) is degrading at present under the influence of Global Warming，which will greatly affect the stability of engineering structures and the ecosystem on the QTP. The variation of the air temperature and the process of permafrost degradation based on the air temperature in the permafrost regions on the QTP from 1955 to 2011 from four weather stations along the Qinghai—Tibet railway (QTR) were studied. The continuous ground temperatures over 35 years from two boreholes including a 15-meter- deep borehole on the sunny slope and a 35-meter-deep borehole on the shady slope of the mountain，acquired from the permafrost observational station at Fenghuoshan were analyzed. The annual mean air temperature in the permafrost regions along the QTR started to rise gradually in late 1950s，went down during 1970s，ascended back in the middle of 1980s and increased rapidly after 2000，and the rate of increasing is rising conspicuously. From 1978 to 2014，the annual mean ground temperature of the permafrost on the sunny slope of the Fenghuoshan climbed up by 0.91 ℃，and that on the shady slope also increased by 0.58 ℃ from 1964 to 2014. The permafrost is degrading because of the rising temperature. With the degradation of the permafrost，the type of geothermal temperature curves has transformed. The geothermal temperature curve of the sunny slope was changed from the initial positive geothermal gradient type to zero geothermal gradient type，then to the current minus geothermal gradient type. The geothermal temperature curve of the shady slope was changed from the initial positive geothermal gradient type to the zero geothermal gradient type. The degradation on the sunny slope is far more severe than that on the shady slope，which is mainly caused by the difference of ground temperature in cold seasons. The permafrost table is sensitive to the change of the annual mean air temperature and fluctuates with the climate change.
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2016, Vol. 35 
