Mass balance of Muji Glacier, northeastern Pamir, and its controlling climate factors

The lack of glacier mass balance and meteorological data limit our knowledge of the spatial pattern of glacier changes in the Pamir. Based on meteorological measurements and mass balance records for Muji Glacier in the northeastern Pamir during 2011-2017, the temporal variations in energy and mass balance, and the response of mass balance to climate variations, were investigated using the energy-mass balance model. The model was assessed by the measurements of seasonal mass balance and snow thickness at different altitudes and seasonal glacier-wide mass balance. Results reveal that glacier-wide mass balance was slightly negative (mean: -276 mm w.e. yr(-1)) on Muji Glacier which could readily reach a zero mass balance under the present climatic conditions. In addition, a method is proposed for assessing whether melt-season air temperature (T-a) or precipitation (P) is more important for controlling interannual variability of glacier mass balance on the Tibetan Plateau, based on limited observations. This method is based on sensitivity analysis and the interannual variability of T-a and P, and shows that P (particularly P in the melt season) is a stronger control than T-a on interannual changes in mass balance variations of Muji Glacier, through the influence of P on albedo, melt energy and snow accumulation. In addition, a comparative analysis shows that smaller snowfall (resulting from lower P) and larger melt (linked to higher incoming longwave radiation and T-a) cause the more negative glacier mass balance in the northeastern Pamir than in the western Kunlun mountains.