中文摘要：

天山乌鲁木齐河源多年冻土变化的研究,对于揭示气候变暖背景下,天山多年冻土对气候变化的响应以及由多年冻土变化引起的植被土壤演化、水文变化具有重要意义.对1991以来河源区海拔3500m左右的气温、降水、地温观测数据进行综合分析,结果表明：河源区的活动层呈逐渐增厚趋势,最大活动层厚度出现在2007年,达到1.60m,较1992年增加了0.35m;多年冻土活动层的变化与河源区夏半年（5-10月）的水热状况密切相关,活动层厚度随融化指数、夏半年降水量的增加而增大.多年冻土年变化深度由1993年的10m增加到12m左右;年平均地温上升明显,由1993年的-1.6℃上升到2008年的-1.0℃.年变化层以下的温度,均有不同程度的上升,年均增温速率随深度的增加而减小,推断长期持续的气候变暖是导致乌鲁木齐河源区多年冻土升温的主要驱动力.估算2008年的多年冻土下限深度约为86.8m,较1992年减小了7.7m,河源区多年冻土很可能正在发生自下而上的迅速退化.

英文摘要：

Research on the variation of permafrost in the Headwaters of the Urumqi River in the Tianshan Mountains has great significance for revealing the response of permafrost to climate change and its impact on ecological and hydrological regimes during the period of climate warming. The data used in the study include air temperature,precipitation,and ground temperature at the elevation of 3 500 m in the study area since 1991. The active layer depth has been increasing since 1991. During the study period,the maximum depth （1.6 m） occurred in 2007,0.35 m more than that in 1992. The variation of active layer depth was closely related to the moisture and thermal regime in the summer half year （from May to October）. The active layer depth was positively related with thawing indices and precipitation in the warm season. The depth of annual ground temperature amplitude increased from 10 m in 1993 to 12 m. The annual mean ground temperature increased from -1.6 ℃ in 1993 to -1.0 ℃ in 2008. The annual mean warming rate decreased with depth. Persistent climate warming is probably the major cause of the current permafrost warming in this area. The estimated depth of permafrost base was approximately 86.8 m in 2008,7.7 m less than that in 1992. It is presumed that the permafrost has been degrading rapidly from bottom to top during the latest years,especially after entering the 21st century.