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 degrees C and about half of the permafrost has its temperature higher than -1.0 degrees C. The lowest average permafrost temperature is about -3.8 degrees 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 degrees C per 100 m altitude increase and 0.79 degrees C per latitude moving north. Permafrost temperature gradients change dramatically along the Qinghai-Tibet Highway/Railway, ranging from about 1.0 degrees C/100 m in Liangdaohe basin of southern Plateau to 8.0 degrees C/100 m in Kunlun Mts. area of northern Plateau. Assuming thermal conductivity of 2.0 Wm(- 1) degrees 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. (C) 2010 Elsevier B.V. All rights reserved.