西天山托木尔峰南麓大型山谷冰川冰舌区消融特征分析

基于对托木尔峰南麓托木尔型山谷冰川的野外考察和典型冰川的定位观测,对冰面被表碛广泛覆盖的所谓"托木尔型"冰川冰舌区表碛与冰面消融的关系进行了研究.结果表明:表碛对冰面消融、冰川水文过程、冰川变化等均具有重要影响,当表碛厚度超过3 cm时,表碛对冰面消融就产生明显抑制作用,且随着厚度增加,冰面消融显明减弱.科其喀尔冰川表面的观测表明,由末端向上,表碛厚度逐渐减薄.受表碛影响,科其喀尔冰川区最大的消融量出现在海拔3 800~3 900 m之间、表碛物厚度小于10 cm的区域内;冰川消融强度由此向上随着海拔的升高而下降,向下随表碛厚度的增大而减弱.冰面湖的发育是表碛覆盖冰川的又一主要特征,湖水对冰面的融蚀和快速排泄成为冰面产汇流的主要过程.科其喀尔冰川研究表明,两三个冰面湖排泄形成的融蚀冰量就相当于冰川末端退缩造成的冰量损失.因此,冰面湖等热喀斯特地形的形成、扩张融蚀、融穿排泄、形成湖区低地,这一周而复始的过程不仅是其主要消融方式之一,而且也强烈的影响着冰川水文及冰川变化.托木尔峰南麓地区大型冰川变化主要以厚度减薄为主,而不是像大多数冰川显著的变化主要表现在末端和面积减少方面.

Study of the ice tongue ablation features of a large glacier in the south slopes of the Mt. Tuomuer in the Tianshan Mountains

In this paper, based on observation and expedition, the relationship between ablation and surface debris cover in the tongue area of a large typical valley glacier on the south slopes of Mt. Tuomuer in the Tianshan Mountains has been studied. The surface debris cover is of important impacts on surface ablation, hydrological process of glacier and glacier change. It is revealed that surface debris has obvious inhibiting effect to surface ablation when the depth of surface debris cover is more than 3 cm. The surface ablation of glacier will weaken markedly with increasing the depth of debris cover. Measurement on the surface of the Koxkar Glacier shows that depth of surface debris cover reduces gradually with altitude. Due to the influence of surface debris on surface ablation, the maximum ablation on the Koxkar Glacier appears in the altitude range of 3 800-3 900 m, where the depth of surface debris cover is less 10 cm. Ablation intensity decreases with altitude and reduces with depth of debris cover due to the effect of surface debris. Another pronounced feature of surface debris-cover glacier is that supraglacial lakes develop universally over the ablation area. Supraglacial lake makes melting erosion onto ice and quick draining of lake water, which becomes the main process of runoff yield and conflux. It is found that in the Koxkar Glacier water yield of melting erosion from 2-3 supraglacial lake is equal to the losing ice volume in the glacier terminus per year. These processes, i.e., running in cycle, formation, melting expansion and draining, are produced by thermokarst effect, such as supraglacial lakes, are not only one of important ablation pattern, but also one factor that influences mightily the changes of glacier and glacier hydrological process. Thinning of glacier is primary to the change of the large glaciers in the south slopes of the Mt. Tuomuer, which is unlike to the most glaciers in China, of which changes of glacier terminus and glacierized area are dominating.