Dreidimensionale Modellierung zweier Gletscher und Deformationsanalyse von eisreichem Permafrost
Dreidimensionale Modellierung zweier Gletscher und Deformationsanalyse von eisreichem Permafrost
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永久冻土三维模型和变形分析
DOI：
10.3929/ethz-a-000954695
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发表时间：
1994
影响因子：
4.1
通讯作者：
S. Wagner
中科院分区：
文献类型：
--
作者：
S. Wagner
这项工作的目的是评估一个合适的计算机程序，它可以求解三维冰力学模型描述的微分方程，并对其进行测试，然后将其提交给当前瑞士冰川学研究的实际问题。在蒙特罗萨的Colle Gnifetti，对一个英格化鞍座的流动行为进行了研究。结果表明，鞍座中心区的水流方向可随深度变化，最大可达180°，并受冰川表面和冰床明显不同的地形所制约。根据流场确定了单个冰粒的运动轨迹，并用数值方法计算了两个钻孔获得的岩心的冰龄。将计算结果与冰芯分析研究结果进行了比较。对对称鞍座的二维和三维模型计算结果的比较表明，对于这种冰川几何形状，仅用二维计算结果只在一定条件下是可靠的。在Alteis Seitengletscher上，对夏末每四到五年才能观测到的周期性滑动的条件进行了调查。这样的滑动会引发一种运动学波，这种波可以在几年后观察到。对地表速度的测量清楚地表明，根据季节变化以及每年的变化，表面速度的大小和方向都有变化。利用三维模型计算，考虑了边界条件的季节变化，推导了1985-1991年间的流动和应力场。Alteis Seitengletscher的测量和计算速度之间的比较表明，它全年在海床上滑动，至少部分滑动，夏季更多，冬季更少。通过使用模型计算，可以证明，在上滑动裂缝区域，从一次滑动到下一次滑动，张力增加。然而，最大张力并不完全发生在滑动裂缝处，而是向下约30米处。这可能是由于确定冰川床几何形状的精度不够所致。通过对莫尔特尔(Corvatsch)岩石冰川钻孔的位移测量，确定了富冰多年冻土的本构关系。它表明，在接近熔点的温度下，冰中即使有少量的杂质，也会对其粘性产生很大的影响。
The aim of this work is to evaluate a suitable Computer program, which solves the differential equations of three-dimensional, ice-mechanical model descriptions, and to test it, and then to submit it to actual questions of current glaciological research in Switzerland. At Colle Gnifetti (Monte Rosa), the flow behavior of an englaciezized saddle was examined. It could be shown that the flow direction could change in the central area of the saddle, according to depth, as much as 180° and that it is conditioned by the clearly differing topographies of glacier surface and its bed. According to the flow field, the trajectories of Single ice particles were determined, and with them, by numerical method, the age of ice from cores obtained from two borings could be calculated. The results were compared with those gained by analytical investigations of the ice cores. Comparisons of the results obtained from two and three dimensional model calculations of a symmetrical saddle have shown, that for such glacier geometries, results from calculating with merely two dimensions are only reliable under certain conditions. On the Alteis Seitengletscher, the conditions for the periodic slides, which can only be observed every four to five years during late summer, were investigated. Such slides initiate a kinematic wave, which can be observed for several years after. Measurements of the surface velocity clearly show variations in magnitude and direction, according to seasonal changes, as well as from year to year. Using three dimensional model calculations and accounting for seasonal changes in marginal conditions, the flow and stress field during the years 1985 1991 was deduced. A comparison between measured and calculated velocities of the Alteis Seitengletscher showed that it slides, at least partly, over its bed the whole year through, more in summer, less in winter. By use of the model calculations it could be demonstrated, that in the area of the Upper Slide Crevasse, the tensions increase from one slide to the next. The maximum tension however, does not occur exactly at the Sliding Crevasse but about 30 m downwards. This is probably due to insufficient accuracy in the determmation of the glacier bed geometry. Due to displacement measurements in a bore hole on rock glacier Murtel (Corvatsch), a constitutive law for ice-rich-permafrost was determined. It demonstrates, that at temperatures near melting point, even small quantities of impurity in the ice, have a great influence on its viscous properties.