Geomorphometric Controls on Mountain Glacier Changes Since the Little Ice Age in the Eastern Tien Shan, Central Asia

The linkage between glacier change and climate has garnered significant attention in recent decades, but little is known about the role of local geomorphometric factors on glacier changes since the Little Ice Age (LIA), approximately 100 to 700 years ago. This study examines the spatial pattern of changes in glacier area in the eastern Tien Shan based on geomorphological mapping of LIA glacial extents and contemporary glaciers from the Second Glacier Inventory of China. Partial least squares regression was applied to examine the correlations between geomorphometric factors, including glacier area, slope, aspect, shape, elevation, and hypsometry, and relative glacier area loss, both in the whole area and in three subregions (the Boro-Eren Range, the Bogda Range, and the Karlik Range). Our results show that the area of 640 mapped LIA glaciers decreased from 791.6 ± 18.7 km2 to 483.9 ± 31.2 km2 between 2006 and 2010, a loss of 38.9 ± 2.7 percent. The losses for three subregions are 43.4 ± 3.2 percent, 35.9 ± 2.4 percent, and 30.2 ± 1.8 percent, respectively. Elevation, slope, and area of a glacier are the three most significant geomorphometric factors to glacier area change, at both regional and subregional scales. The west–east decreasing trend of glacier retreat and different variances explained in subregional regressions might reflect the influence from the shifting dominance of the westerlies and the Siberian High.