Changes in glacier mass in the Lenglongling Mountains from 1972 to 2016 based on remote sensing data and modeling

Abstract

Glacial meltwater-fed streamflow from the Qilian Mountains provides a much-needed source of water for the northeastern margins of the Tibetan Plateau (TP) and surrounding regions. We analyzed changes in glaciers located in the Lenglongling Mountains (LLM) in the eastern Qilian Mountains in terms of glacier area and surface elevation. These analyses were accomplished using multi-temporal satellite images and studying digital elevation models (DEMs) based on topographic maps and ZY-3 data. The results showed that from 1972 to 2016, glacier coverage decreased by 41.1 km2, leaving only 62.1 km2 extant in 2016. The mean rate of change in glacier surface elevation asl was −18.7 ± 1.2 m (−0.43 ± 0.03 m a−1) over the same period. In situ measured data from Ningchan No.1 Glacier (NC01), combined with meteorological records, were also employed to develop a spatially distributed degree-day model for the LLM glaciers. These two approaches yielded similar results, allowing the reconstruction of a consistent time series that detailed annual changes in glacier mass over the past 44 years. In addition, we calculated that the mean annual glacial meltwater-fed streamflow from 1972 to 2013 in the Jiutiaoling Basin (JTLB) northeast of the LLM was equivalent to 1.4 × 107 m3, or 4.6% of the area’s total annual streamflow. It is remarkable that, in years when streamflow was relatively lower, such as 1972, 1991 and 2013, glacial meltwater accounted for a higher proportion (more than 8%) of the streamflow.