An investigation of the thermo-mechanical features of Laohugou Glacier No. 12 in Mt. Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model
Yuzhe Wang1,2, Tong Zhang3, Jiawen Ren1, Xiang Qin1, Yushuo Liu1, Weijun Sun4, Jizu Chen1,2, Minghu Ding3, Wentao. Du1,2, and Dahe Qin11State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China 2University of Chinese Academy of Sciences, Beijing 100049, China 3Insititute of Climate System & Polar Meteorology, Chinese Academy of Meteorological Sciences, Beijing 100081, China 4College of Geography and Environment, Shandong Normal University, Jinan 250014, China
Received: 05 Feb 2016 – Accepted for review: 23 Feb 2016 – Discussion started: 04 Mar 2016
Abstract. En-glacial thermal conditions are very important for controlling ice rheology. By combining in situ measurements and a two-dimensional thermo-mechanically coupled ice flow model, we investigate the present thermal status of the largest valley glacier (Laohugou No. 12; LHG12) in Mt. Qilian Shan in the arid region of western China. Our model results suggest that LHG12, previously considered as fully cold, is probably polythermal, with a lower temperate ice layer (approximately 5.4 km long) overlain by an upper layer of cold ice over a large region of the ablation area. Generally, modelled ice surface velocities match in situ observations in the east branch (mainstream) well but clearly underestimate the ice surface velocities near the glacier terminus because the convergent flow of the west branch is ignored. The modelled ice temperatures agree closely with the in situ measurements (with biases less than 0.5 K) from a deep borehole (110 m) in the upper ablation area. The model results were highly sensitive to surface thermal boundary conditions, for example, surface air temperature and near-surface ice temperature. In this study, we suggest using a combination of surface air temperatures and near-surface ice temperatures (following the work of Wohlleben et al., 2009) as Dirichlet surface thermal conditions to include the contributions of the latent heat released during refreezing of surface melt-water in the accumulation zone. Like many other alpine glaciers, strain heating is the most important parameter controlling the en-glacial thermal structure in LHG12.
Wang, Y., Zhang, T., Ren, J., Qin, X., Liu, Y., Sun, W., Chen, J., Ding, M., Du, Wentao., and Qin, D.: An investigation of the thermo-mechanical features of Laohugou Glacier No. 12 in Mt. Qilian Shan, western China, using a two-dimensional first-order flow-band ice flow model, The Cryosphere Discuss., doi:10.5194/tc-2016-38, in review, 2016.