C33E-0881
Permafrost conditions over Heihe River Basin in Qilian Mountains of Western China
Wednesday, 16 December 2015
Poster Hall (Moscone South)
Bin Cao1, Tingjun Zhang1, Xiankai Zhang1, Xiaoqing Peng2, Kang Wang2, Hong Guo1, Lei Zheng3, Qingfeng Wang4, Xudong Wan2, Cuicui Mu2, Jichun Wu5, Huijun Jin4 and Ruixia He6, (1)LZU Lanzhou University, Key Laboratory of Western China's Environmental Systems（Ministry of Education), College of Earth and Environmental Sciences, Lanzhou, China, (2)LZU Lanzhou University, Key Laboratory of Western China's Environmental Systems（Ministry of Education), College of Earth and Environment Sciences, Lanzhou, China, (3)Wuhan University, Chinese Antarctic Center of Surveying and Mapping, Wuhan, China, (4)Chinese Academy of Sciences, State Key Laboratory of Frozen, Cold and Arid Regions Environmental and Engineering Research Institute Soil Engineering, Lanzhou, China, (5)Nanjing University, Nanjing, China, (6)Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China
Abstract:
To investigate the thermal state of permafrost, a monitoring network with 13 boreholes and 5 automatic weather stations was established over the Upper Reaches of Heihe River Basin in Qilian Mountains of western China from 2011 to 2014. The boreholes were drilled along both east-west transects which is parallel to the Qilian Mountain ridges and the north-south transects. These boreholes with elevation from 3642 m a.s.l. to 4153 m a.s.l., covering different facing-slopes, vegetation cover, land cover, and soil types. Five automatic meteorological stations were established with measurements of soil temperatures within the active layer up to 2 m. In the present study, ground penetrating radar (GPR), mechanical probing and site digging methods were also used to detect active layer thickness (ALT) and permafrost distribution over the Upper Reaches of Heihe River Basin. The results showed that the ground temperature between 18 m and 20 m depth ranged from -1.85 °C to 0.45 °C in this area. There was a significant negative correction between elevation and mean annual ground temperature (MAGT), i.e., MAGT increases -0.65°C for every 100 m. The permafrost thickness varies from nearly 200 m to about 4.3 m. Both the ground temperature and permafrost thickness were significantly influenced by slope aspect, vegetation, surface condition, lithology and groundwater. The ALT was 133 cm with a range of 81~210 cm in eastern tributary and varied from 107 cm at the north-facing slope to 484 cm near the lower limit of permafrost with a mean depth of 271 cm in western tributary. The lower limit of permafrost was found at lowest elevation 3389 m and 3649 m on the north- and south-facing slopes, respectively. The near-zero temperature gradients suggested that recent warming had already penetrated into the ground and influenced the thermal state of permafrost significantly.
