Long-range terrestrial laser scanning measurements of summer and annual mass balances for Urumqi Glacier No. 1, eastern Tien Shan, China

Abstract

Abstract. The direct glaciological method typically provides in situ observations of annual or seasonal surface mass balance, but can only be implemented through a succession of intensive in situ measurements of measuring networks of stakes and snow pits. This has contributed to glacier surface mass-balance measurements being sparse and often discontinuous in the Tien Shan. Nevertheless, long-term glacier mass-balance measurements are the basis for understanding climate–glacier interactions and projecting future water availability for glacierized catchments in the Tien Shan. Riegl VZ®-6000 long-range terrestrial laser scanning (TLS), typically using class 3B laser beams, is exceptionally well suited for measuring snowy and icy terrain in repeated glacier mapping, and subsequently annual and seasonal geodetic mass balance can be determined. This paper introduces the applied TLS for monitoring summer and annual surface elevation and geodetic mass changes of Urumqi Glacier No. 1 (UG1) as well as delineating accurate glacier boundaries for two consecutive years (2015-17), and discusses the potential of such technology in glaciological applications. Three-dimensional changes of ice and firn/snow bodies and the corresponding densities were considered for the volume-to-mass conversion. UG1 showed pronounced thinning and mass loss for the four investigated periods; glacier-wide geodetic mass balance in the mass-balance year 2015-16 was slightly more negative than in 2016-17. The majority of TLS-derived geodetic elevation changes at individual stakes were slightly positive, but showed a close correlation with the glaciological elevation changes (changes in exposed stake height) of individual stakes (R2 ≥ 0.90). Statistical comparison shows that agreement between the glaciological and geodetic mass balances can be considered satisfying, indicating that the TLS system yields accurate results and has the potential to monitor remote and inaccessible glacier areas where no glaciological measurements are available.

Spatial Distribution and Scaling Properties of Lidar‐Derived Snow Depth in the Extratropical Andes

“…The location of the scanner at each date was measured using a Trimble R4 Real Time Kinematic (RTK) point, providing an absolute position uncertainty of 0.01 and 0.03 m in the horizontal and vertical directions, respectively. We processed each individual point cloud using Riegl Riscan Pro V. 2.5.1, following a manual point‐to‐point feature matching to coarsely align the cloud and a subsequent iterative cloud matching algorithm (Chunhai Xu et al, 2018) for precise alignment of snow free, stable terrain. Errors of the iterative process were between 0.02–0.04 m, indicating a successful cloud matching result.…”

Detecting of Cave Floor Ice Dynamics based on Selective Cloud-to-Cloud Approach

“…However, use of TLS in ice caves is more challenging for the slippery surface, harsh climate and reflectance of the ice absorbing much of the laser energy emitted by the scanner (Kamintzis et al, 2018). Examples of using TLS in glaciers and ice (Bauer et al, 2003;Avian and Bauer, 2006;Gašinec et al, 2012;Gabbud et al, 2015;Fischer et al, 2016;Xu et al, 2018) and snow depth change (Jörg et al, 2006;Kaasalainen et al, 2008;Prokop, 2008;Deems et al, 2013). Gómez-Lende and Sánchez-Fernández (2018) demonstrate potential of (TLS) technology in the mapping of ice accumulations in the caves.…”