Response of glacier mass balance to climate change in the Tianshan Mountains during the second half of the twentieth century

Abstract

Systematic differences in glacier mass balance response to climate warming are apparent in the Tianshan Mountains, which are primarily caused by different climatic regimes and glacier hypsography. Combined mass balance data of nine monitored glaciers in the Tianshan Mountains shows that most glaciers accelerated their mass losing rate since 1970s (averaged from −24.6 mm w.e. a⁻¹ in 1957–1970 to −444.6 mm w.e. a⁻¹ in 1971–2009), but also exhibiting discrepancy and consistency during the second half of the twentieth century. To see their climatic–mass balance relationships, we employ a simple temperature index mass balance model on five well monitored glaciers in Tianshan. The model is calibrated by the observed annual, summer and winter mass balance data over the period of 1957–1980 and validated over 1981–2002. A comparison of modeled and measured annual mass balance yields an overall standard deviation of 0.465 m w.e. during the period of model runs. The calibrated mass balance model is also used to perform sensitivity experiments, which indicates the significant differences of individual glaciers in response to climate changes. This study, for the first time, tests a temperature index mass balance model on the selected observed glaciers in the Tianshan Mountains. Although there exists considerable uncertainties, we propose its potential possibility of improvement and applicability for regional glacier mass balance reconstructions and future predictions.