Multi-decadal mass balance series of three Kyrgyz glaciers inferred from transient snowline observations

Glacier mass balance observations in the Tien Shan and Pamir mountains are sparse and often discontinuous. Nevertheless, glaciers are one of the most important components of the high-mountain cryosphere in the region; they strongly influence water availability in the arid, continental and intensely populated downstream areas. This study provides reliable and continuous mass balance series for selected glaciers located in the Tien Shan and Pamir-Alay. A combination of three independent methods was used to reconstruct for the past two decades the mass balance of the three benchmark glaciers, Abramov, Golubin and No. 354. By applying different approaches, it was possible to compensate for the limitations and shortcomings of each individual method. This study proposes the use of transient snowline observations throughout the melting season obtained from satellite imagery and terrestrial automatic cameras. By combining modelling with remotely acquired information on summer snow depletion, it was possible to infer glacier mass changes for unmeasured years. Multi-annual mass changes based on high accuracy digital elevation models and in situ glaciological surveys were used to validate the results for the investigated glaciers. Substantial mass loss was confirmed for the three studied glaciers by all three methods, ranging from −0.30 ± 0.19 m w. e. a −1 to −0.41 ± 0.33 m w. e. a −1 over the 2004–2016 period. Our results indicate that integration of snowline observations into mass balance modelling significantly narrows the uncertainty ranges of the estimates, and hence highlights the potential of the methodology for application to inaccessible glaciers at larger scales for which no direct measurements are available.