Responses of Permafrost on the Qinghai-Tibet Plateau, China, to Climate Change and Engineering Construction

Monitoring of permafrost along the Qinghai-Tibet (Xizang) Highway shows that there is a large difference in the response of permafrost to climate change and to engineering construction. The change in cold (,21.5uC) permafrost is greater than that in warm ($21.5uC) permafrost under the effect of climate change, while the cold permafrost is less sensitive to the disturbances from engineering activities. However, warm permafrost is very sensitive to both climate warming and the impacts from engineering construction. This is because engineering construction has more immediate and direct impacts on the thermal and moisture regimes of underlying permafrost, and consequently greater influence than climate change during the first few years after engineering construction. Assuming constant annual rates of warming, the surface of cold permafrost would approach the warming due to engineering construction in 50 yr, while it would take about 20 yr in areas with warm permafrost. At a depth of 6 m, the temperature rise under engineered surfaces would be reached within 20 and 5–8 yr in cold and warm permafrost, respectively. Therefore, the warming immediately following disturbances of engineering construction would occur naturally in a few years under warm permafrost, but it would take decades for cold permafrost to have the similar thermal effects. Therefore, climate change will have more direct and immediate impacts on the thermal regime of warm permafrost and on the stability and reliability of engineering infrastructures above warm permafrost.