Abstract
The seasonal surface changes of glaciers in Tien Shan have seen little prior investigation despite the increase in geodetic studies of multi-year changes. In this study, we analyzed the potential of an Unmanned Aerial Vehicle (UAV) to analyze seasonal surface change processes of the Urumqi Glacier No. 1 in eastern Tien Shan. We carried out UAV surveys at the beginning and the end of the ablation period in 2018. The high-precision evolution of surface elevation, geodetic mass changes, surface velocity, and terminus change in the surveyed ablation area were correspondingly derived in combination with ground measurements, including stake/snow-pit observation and GPS measurement. The derived mean elevation change in the surveyed ablation area was −1.64 m, corresponding to the geodetic mass balance of approximately −1.39 m w.e. during the ablation period in 2018. The mean surface velocity was 3.3 m/yr and characterized by the spatial change of the velocity, which was less in the East Branch than in the West Branch. The UAV survey results were a little less than those from the ground measurements, and the correlation coefficient was 0.88 for the surface elevation change and 0.87 for surface displacement. The relative error of the glacier terminus change was 4.5% for the East Branch and 6.2% for the West Branch. These results show that UAV photogrammetry is ideal for assessing seasonal glacier surface changes and has a potential application in the monitoring of detailed glacier changes.
Highlights
The glacier, one of the core elements of the cryosphere, is a natural indicator of climate change [1,2]
−0.4 m during the period from 24 April to 26 August 2018 based on the two Unmanned Aerial Vehicle (UAV) surveys (Figure 5a)
From two UAV flights, the high-precision evolution of surface elevation was obtained; the geodetic mass was subsequently converted according to snow density conversion
Summary
The glacier, one of the core elements of the cryosphere, is a natural indicator of climate change [1,2]. It is important to investigate glacier change processes on different scales with various methods. In situ observation is the basis for understanding the response of glaciers to climate and for predicting the future changes in glaciers [9,10]. As the direct linkage between glacier and climate change, the change in mass balance is the primary observational item. The traditional method of glacier mass balance measurement is based on the stake/pit observation, which is labor and time consuming but topographically limited. The comparison of glacier surface elevations between two or more surveys can provide the mass balance change during the survey period and is regarded as the geodetic method
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