Application of a distributed degree-day model of glaciers in the upper reaches of the Beida River Basin

Abstract

Based on in-situ data of Qiyi Glacier from 2010 to 2012, a daily distributed degree-day model on a 90 × 90 m grid was developed to simulate the spatial and temporal variations of the glacier mass balance, ELA, and meltwater run-off depth in the Beida River Basin from 1957 to 2012. In the model, different vertical lapse rates of temperature and precipitation gradients were used in different months and height-belts, and the influence of ‘temperature jump’ was also considered. The results indicated that the average annual mass balance and meltwater run-off depth of the glaciers in the Beida River Basin were −93.3 mm w. e. and 443 mm, respectively. Assuming a continuous linear trend, the ELA had risen by 505 m over 55 years. The mass balance linearly increased with the altitude in the cold season (Oct.–Apr.) and exponentially in the warm season (May–Sep.). The most possible abrupt change points of the mass balance, ELA, and meltwater run-off depth time series were all in 1992/93, as determined through the M–K test. The mass balance turned increasingly negative since then, but the ELA and meltwater run-off increased rapidly. The climate sensitivity test showed that the air temperature was a dominant factor that affected the mass balance of the continental glaciers on the basin scale, which was different from the response mechanism of maritime glaciers. When the air temperature (+1 °C) and precipitation (+10 %) increased simultaneously, the glacier mass loss and meltwater run-off reached 1.66 × 108 m3 and 2.45 × 108 m3, respectively.