Permafrost temperatures and thickness on the Qinghai-Tibet Plateau

Based on permafrost temperature measurements from 190 boreholes along the Qinghai-Tibet Highway/Railway since the early 1960s, we present spatial variations of permafrost temperatures, thermal gradients, and thickness on the Qinghai-Tibet Plateau. Overall, permafrost temperatures at 15 m depth are higher than − 4.0 °C and about half of the permafrost has its temperature higher than − 1.0 °C. The lowest average permafrost temperature is about − 3.8 °C in the Fenghuo Mts. area. Permafrost temperatures are strongly controlled by elevation and latitude on the Qinghai-Tibet Plateau. Permafrost temperatures at 15 m depth decrease at a rate of 0.57 °C per 100 m altitude increase and 0.79 °C per latitude moving north. Permafrost temperature gradients change dramatically along the Qinghai-Tibet Highway/Railway, ranging from about 1.0 °C/100 m in Liangdaohe basin of southern Plateau to 8.0 °C/100 m in Kunlun Mts. area of northern Plateau. Assuming thermal conductivity of 2.0 Wm − 1 °C − 1 of bedrocks at depth, geothermal heat flux varies from 0.02 Wm − 2 to 0.16 Wm − 2 . Permafrost thickness ranges from less than 10 m to over 300 m along the Qinghai-Tibet Highway/Railway. Besides elevation and latitude, geothermal heat flux also plays a key role in controlling permafrost temperature and thickness.