PROGRESS IN GEOGRAPHY ›› 2011, Vol. 30 ›› Issue (7): 827-836.doi: 10.11820/dlkxjz.2011.07.007

• Original Articles • Previous Articles     Next Articles

Characteristics of Ground Temperatures and Influencing Factors of Permafrost Development and Distribution in the Source Region of Datong River

LI Jing, SHENG Yu, CHEN Ji, ZHANG Bo, WU Jichun, ZHANG Xiumin   

  1. State Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute, CAS, Lanzhou 730000, China
  • Received:2011-01-01 Revised:2011-04-01 Online:2011-07-25 Published:2011-07-25

Abstract: Permafrost is thermally defined as the ground where temperatures have remained at or below 0℃ for a period of at least two consecutive years. Ground temperatures at depth were a valid index to make knowledge of permafrost thermal regimes and permafrost development at certain locations. Based on 39 borehole data, drilled in the summers of 2007 and 2009 at different elevations with representatives of surface characteristics of topography, geomorphology, landcover, vegetation and soil water content, and the measured ground temperatures in the source region of Datong River in the northeast Qilian Mountains, the characteristics of ground temperatures at depth at the drilling sites were analyzed using the temperature profiles, and the main factors controlling permafrost temperatures and distribution in the study area were primarily summarized. Elevation and the elevation- dependant MAAT (mean annual air temperature) determined the climate settings of the region and the macro-scale permafrost distribution and temperatures patterns, and thus were the first-order factors affecting permafrost temperatures in the source region. In the local- or micro-scale areas in low- and mid-elevation zones (elevation generally lower than 3800 m), however, the landcover conditions (vegetated area, bare ground or exposed rock), the vegetation type (the alpine meadow or the swampy alpine meadow), and the topsoil water content (saturation or oversaturation) had some important impacts on permafrost temperatures, which could affect the permafrost occurrence at certain locations and lead to the spatial differentiation of permafrost distribution. In high-elevation zones (elevation usually exceeds 4000 m), elevation alone could determine the presence of permafrost, and the local factors had effects on the gradient of permafrost temperatures with depth. The result could be as the basis of understanding the permafrost stability, and permafrost change or degradation under the climatic warming, also could provide the knowledge to the relevant studies of climatic changes, ecology, and hydrology in cold regions.

Key words: characteristics of permafrost ground temperatures, influencing factors, permafrost, the source region of Datong River