The Response Model of Permafrost along the Qinghai-Tibetan Highway under Climate Change
WU Qing bai 1, 2 , LI Xin 1, LI Wen jun 1 (1.State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China; 2.Earth Science Department of Nanjing University, Nanjing Jiangsu 210093, China)
GCM model HADCM2, which was developed in the Hadley Center for Climate Prediction and Research in Britain, was adopted for climate scenarios. Only air temperature scenarios in permafrost response model are used. In order to preserve the original air temperature forecast results in the HADCM2; the nearest-neighbor method was used to resample the air temperature for the years 2009, 2049 and 2099 into 0.5°×0.5°grids compatible with the DEM. The predication shows that the mean raising of air temperature will be 0 46 ℃ in 2009, 0 78 ℃ in 2049 and 2 53 ℃ in 2099 from 36° to 33 5° N, and 0 72 ℃ in 2009, 0 78 ℃ in 2049 and 2 68 ℃ in 2099 from 33 5° to 31° N. Altitude model, which was proposed for the permafrost distribution limit in Northern Hemisphere, is used to determine the permafrost distribution limit (Equation 1). Permafrost zone model, which is proposed by the multiple linear regression relationships among MGATs, altitude and latitude, is used to determine the permafrost zone distribution (Equation 2). The altitude model does not contain climate variables, such as air temperature. Thus, the relationship between predicted air temperature change Δ T of HADCM2 and permafrost lower limit uplifting Δ H is established as Equation 3. The relationship between the MAGTs and MAATs can be established as Equation 4. And assuming that rising air temperature would result in immediate permafrost warming. The rising MAATs at lower limit will result in changing MAGTs of permafrost zones. The response model of permafrost zone is proposed on the Equations (3) and (5): Under the support of GIS, the response model of permafrost zone and the DTM along the Qinghai-Tibetan Highway, the permafrost change of the highway are obtained under GCM climate scenario in 2009, 2049, and 2099. The results show that permafrost zone will greatly change after climate warming. Their area is expected to decrease and permafrost zone will be moving upward and degrading. In order to easily discussing permafrost zone change, the relative changes of permafrost zones including 30 km nearby the highway are considered. The area of extreme stable zone will shrink from 5.59% at present to 0.65% in 2099, stable zone from 16 32% in present to 3 28% in 2099, and sub stable zone from 25 5% in present to 17 43% in 2099. Area will increase with air temperature raising for transition zone and unstable zone. Area of transition zone will change from 22 85% at present to 31 01% in 2099 and that of unstable zone from 10 8% at present to 27 46% in 2099. Extreme stable zone will transform into stable zone, stable zone into sub stable zone, sub stable zone into transition zone, transition zone into unstable zone and unstable zone will be in the stage of degradation.