Modelled mass balance of Xibu glacier, Tibetan Plateau: sensitivity to climate change

Due to a lack of in situ measurements, model-based studies of glacier mass balance in the Tibetan Plateau are very limited. An energy-balance model is applied to analyse the mass-balance sensitivity of Xibu glacier, in the Nyainqentanglha mountain range, to climatic change. A sensitivity calculation shows that a temperature change of +/- 1 degrees C or a precipitation change of +/- 35% changes the equilibrium-line altitude (ELA) by 140 +/- 125 m. We use a clustering method to link local weather parameters, including wet-season temperatures, to weather types observed over the period 1955-2006. Modelled variability of the Xibu glacier mass balance seems to be controlled by air-temperature variations during the wet season (May-September) and by a long-term warming trend that is unrelated to weather type. The observed wet-season temperature trend of 0.23 degrees C (10 a)(-1) leads to an estimated lengthening of the ablation season by 8 days at the glacier terminus (5000 m a.s.I.) and by 23 days at the ELA (5590 m a.s.I.) over the period 1966-2005. The calculated rise in the ELA was 49 m (10 a)(-1).