Changes in the elevation and extent of two glaciers along the Yanglonghe river, Qilian Shan, China

We use topographic maps, historical data, multispectral satellite data and real-time kinematic GPS data to analyze glacier area, length and ice-elevation changes of two glaciers in the central Qilian Shan, China, between 1956 and 2007. We find that the fronts of Yanglonghe glacier No. 1 (5Y432A1) and Yanglonghe glacier No. 5 (5Y432A5) have retreated by 266.5 +/- 37.1 m (5.2 +/- 0.73 m a(-1)) and 181.4 +/- 37.1 m (3.6 +/- 0.73 m a(-1)) respectively, and that this retreat accelerated after 1999. During the study period, the glacier areas decreased by similar to 4.1% and 15.9% respectively. In addition, spatially non-uniform thinning, which averaged 20.2 +/- 11 m (0.4 +/- 0.22 m a(-1)) and 16.9 +/- 11 m (0.33 +/- 0.22 m a(-1)) in the ablation areas of 5Y432A1 and 5Y432A5 respectively, is observed using digital elevation models constructed using data from 1956, 1977 and 2007. The ice-volume depletion from 5Y432A1 (2.91 x 10(7)m(3)) was 2.7 times greater than from the smaller 5Y432A5 (1.08 x 10(7)m(3)). Based on records from nearby Tuole weather station, increasing annual temperatures are principally responsible for the observed glacier thinning and retreat.