Variations in the equilibrium line altitude of Urumqi Glacier No.1, Tianshan Mountains, over the past 50 years

The glacier ELA is one of the important parameters reflecting climate change. Based on observations of the equilibrium line altitude (ELA) of Urumqi Glacier No.1 in the Tianshan Mountains, we established a statistical model between ELA and its major influencing factors, warm season air temperature (air temperature averages for May, June, July and August) and annual precipitation. Result showed that, warm season air temperature was the leading climatic factor influencing ELA variations. The glacier ELA ascends (descends) 61.7 m when warm season air temperature increases (decreases) by 1A degrees C, and ascends (descends) 13.1 m when cold season precipitation decreases (increases) by 10%. In the period 1959-2008, the glacier ELA showed a general increasing trend, ascending108 m and reaching its highest altitude in 2008 at 4168 m a.s.l., close to the glacier summit. If future climate is similar to that in the past 50 years, the ELA of Urumqi Glacier No.1 will still ascend with a speed of 2.16 m/a. However, If future climate is similar to that in the period 2000-2008, the ELA will still ascend with a speed of 6.5 m/a before it is stable. As a result of ELA variation, the accumulation area ratio (AAR) of the glacier showed a decreasing trend during the past 50 years.