Using an ultra-long-range terrestrial laser scanner to monitor the net mass balance of Urumqi Glacier No. 1, eastern Tien Shan, China, at the monthly scale

Abstract

ABSTRACTWe describe the use of a terrestrial laser scanner (TLS) to monitor the net mass balance of Urumqi Glacier No. 1, eastern Tien Shan. We used an ultra-long-range Riegl VZ®-6000 TLS, which is specially designed for surveying snow- and ice-covered terrain, to create repeated high spatiotemporal resolution DEMs, focusing on the monthly-scale (25 April–28 May 2015) net mass balance. According to the TLS-derived DEMs, the area of Urumqi Glacier No. 1 was 1.558 km2on 25 April 2015 and the average surface elevation change was 0.225 m. By comparing the results from the use of TLS with the conventional glaciological mass-balance method, the correlation coefficient (R2) between glaciological elevation changes of individual stakes and the TLS-derived geodetic elevation change of corresponding points was 0.85. Considering the uncertainty of both methods, this is a promising result. Using the in situ measured snow densities (snow pits) of the glacier surface, the geodetic net mass balance was 0.074 m w.e., which is slightly positive. The mean uncertainty in the TLS-derived monthly net mass balance was 0.018 m w.e., showing that the TLS surveying system presented accurate and relevant results and is therefore suitable to monitor mass-balance evolution of mountain glaciers.