Accelerated thinning of Hei Valley No. 8 Glacier in the Tianshan Mountains, China

Abstract

Two field surveys on the thickness of Hei Valley No. 8 Glacier (H8) on the southern slope of Mount Bogda in the Tianshan (天山) Mountains using ground-penetration radar (GPR) were carried out in August 2008 and September 2009. Comparisons of the observed change in glacier thickness using GPR and ablation stakes suggest that GPR observations have high accuracy. Thus, the thickness change for H8 during 2008–2009 was estimated using GPR data. Digital elevation models obtained from topographic maps and the Shuttle Radar Topography Mission were used to analyze ice-elevation changes of H8 between 1 969 and 2 000 m a.s.l.. The results show that H8 has continually thinned, and the thinning rate has increased gradually. The thinning of ablation areas of H8 increased from 0.42±0.56 m/a in 1969–2000 to 1.47±0.79 m/a in 2000–2008, and then accelerated to 1.92±0.98 m/a in 2008–2009. The retreat of the glacier terminus has had a similar pattern. The distribution of the temperate-ice zone of H8 as determined from GPR data also implies that H8 has experienced strong melting from 2008 to 2009, which indicates that temperature rises have not only enhanced glacial surface melting and prolonged melting periods, but also changed the englacial structure and increased the water content of glacier, both of which probably lead to the acceleration of glacial thinning.