底部剪切应力影响因素及其在中国西部冰川研究中的取值

Influencing factors and values of the basal shear stress in glaciers in western China

作为冰川动力学重要参数之一的底部剪切应力,受冰川自身属性以及冰-岩界面条件等多种因素控制,但这些因素能驱使该参数发生何种及多大幅度变化却仍不明晰,阻碍了冰川动力学模型可靠性和精度的提升.本研究借助相关公式和中国西部14条山地冰川的冰面、冰床高程数据,计算冰川底部剪切应力并分析其特征.结果显示,冰川底部剪切应力主要受冰川形态类型控制,呈现冰斗-山谷冰川、山谷冰川、冰斗冰川和坡面冰川依次减小的规律;冰川性质是底部剪切应力的次一级影响因素,表现为同一冰川形态类型时,海洋型冰川的底部剪切应力明显高于极大陆型和亚大陆型.在相关研究中,山地冰川底部剪切应力取值首先应考虑冰川形态,再适当关注冰川性质的差异.

The basal shear stress,an important parameter of glacial dynamics,is determined by various factors such as the properties of a glacier and the ice-rock interface.It is not possible to elucidate the quantitative effect and relevance of these factors,thus hindering the improvement of the reliability and accuracy of the glacier dynamics models.These effect factors were systematically summarized via an analysis of the characteristics of the basal shear stress using relevant formulas and data on ice surface and ice bed elevation from 14 mountain glaciers in western China.The results showed that the basal shear stress was mainly controlled by the glaciers’morphology,with the cirque-valley glacier,valley glacier,slope glacier and cirque glacier in a successively diminishing manner.The properties of glaciers displayed a secondary impact on it.In the same morphology,the basal shear stress of marine glaciers was significantly higher than that of the ultra-continental and sub-continental glaciers.These results highlighted the fact that the morphology of glaciers on the basal shear stress should be considered first,and the miscellaneous glacier properties be properly taken into account in relevant research.