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Originating in the Tian Shan mountains, Urumqi River plays a key role in terms of water supply to downstream areas. In its headwaters, Urumqi Glacier No. 1 (UG1) is the largest glacier contributing to water discharge. Assessing its response to the changing climatic conditions in the area is of major importance to quantify future water availability. We here apply COSIPY, a COupled Snowpack and Ice surface energy and mass balance model in PYthon, to UG1, implementing a new albedo parameterization which integrates site-specific bare-ice albedo values on a pixel-by-pixel basis observed by remote sensing. We assess model performance threefold: quantitatively based on long-term measurement data of (1) surface mass balance (SMB) and (2) water discharge as well as qualitatively (3) comparing simulated snow line altitudes to such imated on the basis of time-lapse photography. Comparison of the modeled SMB with annually-averaged data from ablation stakes reveals that COSIPY including the new albedo parameterization accounts for 57.6% of the variance observed in the measurements. The original albedo parameterization performs only slightly inferior (57.1%). Glacier-wide comparison between modeled and glaciological SMB shows high agreement. In terms of discharge prediction, COSIPY reproduces onset and duration of the discharge season well. Estimated discharge from the whole catchment shows shortcomings in exactly matching the measured times series, but interannual variability is captured. [ABSTRACT FROM AUTHOR]

Abstract The mass balance of Urumqi Glacier No.1, eastern Tien Shan, has been monitored since 1959, using the direct glaciological method. This study presents a detailed comparison of the glaciological mass balance with a high-quality product of geodetic surveys in the overlapping period from 1981 to 2015. We analyzed the generic differences between glaciological and geodetic mass-balance measurements, including in-depth uncertainties assessments. The statistical comparison shows that the reduced discrepancy (δ = 0.53) between the geodetic mass balance (−0.53 ± 0.14 m w.e. a−1) and corrected annul glaciological mass balances (−0.46 ± 0.14 m w.e. a−1) falls within the 95% confidence interval and reveals that no statistical significant bias between the two datasets is detectable over the period. Thanks to the good agreement, calibration of the glaciological to the geodetic data series is currently not required. The more negative geodetic mass balance is probably relevant to the glacier surface characteristics. The uncertainty of our results measured with geodetic method was close to the majority of similar studies, but bigger than those derived from multi-temporal high-quality DEMs. Further studies should continue using a long-range terrestrial laser scanning (TLS) system to derive high-resolution and -precision digital elevation models (DEMs) of the glacier surface at the monthly time-scale, which will provide a powerful complement to the glaciological measurements. Highlights • No statistical significant bias between the geodetic and glaciological mass balance of Urumqi Glacier No.1 is detectable. • A calibration of the glaciological data series is currently not required. • Further studies should continue using a long-range terrestrial laser scannner to monitor the glacier mass balance. [ABSTRACT FROM AUTHOR]

The importance of glaciers for providing runoff is reflected in the extensive glacier measurement record for China. In this paper, we summarized the mass-balance and front-variation data of glaciers in China that have long-term records. Mass balance has been measured for 22 glaciers; length (or front-position) records exist for 96 glaciers. We found that the mean rate of glacial mass balance decreased by −0.015 m w.e. (water equivalent) per year during the period 1959–2015, which was lower than that for glaciers globally (−0.013 m w.e. per year). It was indicated that the rate of glacial melting (mass loss) increased in China, which was higher than that in glaciers worldwide. However, glacial frontal positions varied among mountains in time and space. Glaciers in the Karakoram Mountains mean advanced 379 m during the 1968–2000 period, while glaciers in the Pamir Mountains remained relatively stable from the 1960s through the 2000s, i.e., retreated 28 m. Glaciers in Hengduan Mountains retreated farthest (1250 m maximum) from 1930 to 2005. [ABSTRACT FROM AUTHOR]