As a solid reservoir, a glacier can regulate regional water resources. The annual net mass balance directly reflects the fluctuation of the glacier and climate variability. Based on 51years of mass balance observation data, the mass balance of Tianshan Mountains Urumqi Glacier No. 1 experienced a nine times positive balance fluctuation and nine times negative balance fluctuation. There were 35 and 16negative and positive balance years, respectively. From 1996/97 to 2008/09, 12 consecutive negative balance years were observed at Tianshan Mountains Urumqi Glacier No. 1. These results demon-strate that the Urumqi Glacier No. 1 is experiencing a strong negative balance, and the strongest negative balance, ?931 mm w.e. (mm water equivalent), during the observation period occurred in 2008. In addition, the cumulative mass balance reached 13,709 mm w.e. in 2008. However, in 2009, the mass balance was positive at 63 mm w.e. The equilibrium-line al-titude changes with the fluctuation in the mass balance, and the effective mass balance gradient is 7.4 mm/m. In this study,the headwaters of the Urumqi River were analyzed using meteorological data from 1958 to 2009, including the average seasonal temperature and precipitation. The results showed that the main factor associated with the mass balance variation of Glacier No. 1 is the fluctuation in the summer air temperature, followed by changes in the precipitation.

This research was supported by the National Natural Science Foundation of China (Grant Nos. 41001040 and J0630966), the Foundation for Excellent Youth Scholars of CAREERI (No. 51Y084911), the Knowledge Innova-tion Project of the Chinese Academy of Sciences (KZCX2-EW-311), and the National Basic Research Program of China (2010CB951003).

Sketch of study area