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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2016-38
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
04 Mar 2016
Review status
A revision of this discussion paper for further review has not been submitted.
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 Qin1 1State 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
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.

Citation: 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., https://doi.org/10.5194/tc-2016-38, in review, 2016.
Yuzhe Wang et al.
Yuzhe Wang et al.

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Short summary
We combine in-situ measurements and a ice flow model to study the thermomechanical features of Laohugou Glacier No. 12, the largest valley glacier in Mt. Qilian Shan.

We reveal that this glacier, once considered to be extremely-continental or cold, is actually polythermal with a lower temperate ice layer over a large region of the ablation area. Strain heating and latent heat due to meltwater refreezing in the firn zone play critical roles in controlling the thermal regime of this glacier.
We combine in-situ measurements and a ice flow model to study the thermomechanical features of...
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