西南极洲纳尔逊冰帽的表面运动

THE SURFACE FLOW OF NELSON ICE CAP, WEST ANTARCTICA

本文通过对纳尔逊冰帽冰面速度和应变率的分析,得出冰帽边缘的最大夏季表面速度为2058m/a,最大年平均表面速度为15.5m/a,探求了冰面运动速度的空间分布和季节性变化,冰帽顶部的表面应变率为+0.0079/a和+0.0034/a。还讨论了冰面应变率从冰帽顶点到边缘的变化特点及其与冰面裂隙的关系。并将这些特征同我国大陆型冰帽进行了对比,从冰川动力学的角度阐明了纳尔逊冰帽的某些特征。

In the present paper, authors analysed the spacial distributions and seasonal variation of the surface flow velocities of Nelson ice cap, the non-verticality between the flow vector and the contour at the same point, then explained the strain-rates along profiles N and E through the highest point on the surface of Nelson ice cap and the relation between the strain-rates and crevasses. Finally, authors compared these characteristics to the continental ice caps in China in order to show the marine features of Nelson ice cap in glacier dynamics. The following conclusions could be reached with those mentioned above: 1. The surface flow velocities become large gradually from the highest point to the edge of Nelson ice cap, and get their maximum at the edge. The summer velocities, which are 20.6 m/a and 18.6 m/a at the termini of Profile N and Profile E respectively, are higher than the maximum velocities on the continental ice caps. The mean annual velocities take 66-88% of the summer velocities. Spacially, the more close to the edge, the more the velocity vectors direct down to the surface. Therefore, it can be concluded that the balance equilibrium line appears near to the edge, or, ice-falls to sea water play an important role in the ablation of the ice cap. 2. The principal strain-rates are positive at the top of Nelson ice cap, 1 and 2 are +0.0079/a and +0.0034/a, respectively. 3. The limit of the principal extension strain-rates for the appearance of the ice crevasses on the surface is +0.007/a, on Profile N, and +0.0122/a on Profile E respectively.