Permafrost in the source of Urumuqi River is degrading rapidly

Scientists from the Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), CAS investigated the permafrost variations in the Tianshan source area of the Urumuqi River. By analyzing of the long-time air temperature, precipitation and ground temperature data observed in the riverhead area since 1991 , researchers found that the active layer of the permafrost in the this area exhibited a gradually thickening trend. The largest thickness of active layer occurred in 2007, reaching up to 1.60m, an increase of 0.35m compared with 1992. The variations of active layer of the permafrost were closely related to the water-head conditions from May to October, and the thickness of active layer increased with increasing thawing index and summer precipitation. The annual variation of permafrost depth increased by 12m or so since 1993, and the mean annual ground temperature significantly increased from -1.6℃ in 1993 to -1.0℃ in 2008.

The results also showed that the climate warming is the main driving force for the permafrost degradation in the source area of the Urumuqi River. It was estimated that the permafrost base was about 86.8m in 2008, which was decreased by 7.7m compared with 1992. This study has an important significance to reveal the response of the permafrost to global warming in the Tianshan region even worldwide.