【摘要】 亚极地型的天山乌鲁木齐河源1号冰川底部,存在着三种流动方式:1)底面滑动;2)底碛的变形;3)穿过底碛内剪切面或剪切带的运动。这三种机制作用于冰川最底层1—2％的有效厚度内,它们单独或互相结合的运动占冰川全部运动的70％以上。更多还原

【Abstract】 In a tunnel at the base of the subpolar Urumqi Glacier No. 1, China, three new mechanisms of glacier flow have been observed at subfreezing temperatures. Taken individually or in combination, these modes of flow can account for nearly all (60-80%) of the overall glacier motion and, yet, they act only within the lowermost one to two percent of the effective glacier thickness.These mechanisms are: (1) Enhanced deformation of the frozen and ice-laden subglaciai drift; (2) Motion across discrete shear planes or shear bands within the frozen drift or at the ice-drift interface; and (3) basal sliding at an ice-rock interface at a temperature of nearly -5C The ice-laden drift has an effective viscosity of more than one hundred times less than that measured in the overlying ice, thus allowing very rapid shear deformation. The observed rate of basal sliding at the ice-rock interface agrees favorably with that predicted by the recent work of Shreve (1985) if proper account is taken of the measured surface roughness and reduced ice viscosity.更多还原