Modelling mass balance using photogrammetric and geophysical data: a pilot study at Griesgletscher, Swiss Alps
Modelling mass balance using photogrammetric and geophysical data: a pilot study at Griesgletscher, Swiss Alps
复制标题
使用摄影测量和地球物理数据建模质量平衡：瑞士阿尔卑斯山格里斯格莱彻的试点研究
作者：
A. Kääb;M. Funk
摘要 冰川表面的运动学边界条件可用于给出冰川某点的质量平衡，作为表面高程以及水平和垂直速度变化的函数。垂直速度又可以根据基底坡度、基底冰速度和表面应变来估计。在瑞士阿尔卑斯山格里冰川冰舌的一项试点研究中，测试了该关系在模拟全区域冰流和质量平衡分布方面的适用性。计算的关键输入，即全区域表面速度场，是使用新开发的摄影测量技术获得的。冰厚度来自雷达回波探测。误差估计以及与桩测量的比较显示，计算的表面垂直冰速度的平均精度约为 ±0.3 ma-1，计算的质量平衡的平均精度约为 ±0.7 ma-1。由于摄影测量限制和模型固有的敏感性，所应用的模型似乎最适合确定平坦烧蚀区域的区域范围质量平衡和冰流，但迄今为止不太适合陡峭的烧蚀区域和大部分堆积区域。尽管如此，对格里冰川的研究为监测时空冰川质量平衡变化开辟了一个新的、有前景的视角。
Abstract The kinematic boundary condition al the glacier surface can be used to give glacier mass balance at a point as a function of changes in the surface elevation, and of the horizontal and vertical velocities. Vertical velocity can in turn be estimated from basal slope, basal ice velocity and surface strain. In a pilot study on the tongue of Griesgletscher, Swiss Alps, the applicability of the relation for modelling area-wide ice flow and mass-balance distribution is tested. The key input of the calculations, i.e. the area-wide surface velocity field, is obtained using a newly developed photogrammetric technique. Ice thickness is derived from radar-echo soundings. Error estimates and comparisons with stake measurements show an average accuracy of approximately ±0.3 ma-1 for the calculated vertical ice velocity at the surface and ±0.7 ma-1 for the calculated mass balance. Due to photogrammetric restrictions and model-inherent sensitivities the applied model appeared to be most suitable for determining area-wide mass balance and ice flow on flat-lying ablation areas, but is so far not very well suited for steep ablation areas and most parts of accumulation areas. Nevertheless, the study on Griesgletscher opens a new and promising perspective for the monitoring of spatial and temporal glacier mass-balance variations.