Abstract
Ice thickness has a great influence on glacial movement and ablation. Over the course of the change in thickness, area and external climate, the dynamic process of how glaciers change and whether a glacier’s changes in melting tend to be stable or irregular is a problem that needs to be studied in depth. In our study, the changes in the dynamic process of the No. 8 Glacier in Hei Valley (H8) under the conditions of different thicknesses in 1969 and 2009 were simulated based on the Full-Stokes code Elmer/Ice (http://www.csc.fi/elmer/). The results were as follows: (1) The thickness reduction in glaciers would lead to a decrease in ice surface tension and basal pressure and friction at the bottom, and the resulting extensional and compressional flow played an important role in the variations in glacial velocity. (2) The force at the bottom of the glacier was key to maintaining the overall stress balance, and the glaciers that often melted and collapsed in bedrock were more easily destroyed by the overall force balance and increased change rate of glacial thaw. (3) Temperature changes at different altitudes affected the ice viscous force. The closer the ice surface temperature was to the melting point, the greater the influence of temperature changes on the ice viscous force and ice surface velocity. Finally, we used the RCP 4.8 and 8.5 climate models to simulate the changes in H8 over the next 40 years. The results showed that with some decreases in ice surface compression and tension, the gravity component changes caused by local topography begin to control the ice flow movement on the surface of glacier, and melting of the glacial surface will appear as an irregular change. The simulation results further confirmed that the fluctuation in glacial dynamic characteristics could be attributed to the change in the gravity component caused by ablation.
Highlights
Ice thickness has a great influence on glacial movement and ablation
The results showed that with some decreases in ice surface compression and tension, the gravity component changes caused by local topography begin to control the ice flow movement on the surface of glacier, and melting of the glacial surface will appear as an irregular change
The simulation results further confirmed that the fluctuation in glacial dynamic characteristics could be attributed to the change in the gravity component caused by ablation
Summary
Ice thickness has a great influence on glacial movement and ablation. Over the course of the change in thickness, area and external climate, the dynamic process of how glaciers change and whether a glacier’s changes in melting tend to be stable or irregular is a problem that needs to be studied in depth. Researchers have observed many of the glacial changes in the Tianshan Mountains, including glacial area change[5,6,7,8], volume change[9,10,11,12], variation in mass balance[7,13,14,15], runoff characteristics[16,17,18,19] and so on These studies reflect the changes in some factors associated with glacial melting; these studies do not clearly explain the state and potential trends of glaciers based on the mechanism of glacial movement. The diagnostic simulation presented the differences in stress on the surfaces and bottoms of glaciers in 1969 and 2009 The influences of both external and internal factors on glacial movement and ablation were analysed simultaneously. Future change trends of glaciers was discussed, including the effects of dynamic characteristics on ice flow velocity, force, englacial structure and hydrological processes. The climate in this area is a typical continental climate with less precipitation, which is concentrated in summer[32]
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