祁连山老虎沟12号冰川冰内结构特征分析

Structural Characteristics of the No.12 Glacier in Laohugou Valley,Qilian Mountain Based on the Ground Penetrating Radar Combined with FDTD Simulation

利用探地雷达(Ground Penetration Radar,GPR)调查冰川冰内结构和冰层厚度是一种监测冰川变化常用手段。应用麦克斯维(Maxwell)方程的二维时域有限差分(FDTD)方法,通过将模拟图像与老虎沟12号冰川的实测图像的对比,分析了雷达剖面中的几种反射特征,如冰裂隙、融洞、暖冰等。对比结果表明,GPR的反射图像会受到诸多因素的影响,除了介电常数,还包括介质的厚度,形态,粗糙度等因素的影响。探测结果表明,具有极大陆型特征的老虎沟12号冰川的局部的冰内温度呈现出较高的态势。同时,FDTD模拟也为我们未来利用GPR来监测冰川随气候的变化提供了很好的分析手段。

The use of ground penetration radar（GPR）for surveying glacial structure and ice thickness is a common method of monitoring glacial variation,but how to extract accurately the information and ice thickness is often more concerned about data interpretation.In this paper,we have run a Finite-Difference Time-Domain（FDTD） model that solves Maxwell′s equations in two dimensions,by comparison simulated image and the results of measured radar,and analyzed several reflection characteristics within several profiles,such as crevasses,melting cave,and temperate ice and so on.Comparison results show that GPR reflection image is affected by many factors,such as medium thickness,morphology,roughness and other factors as well in addition to dielectric constant.The survey result also shows that the ice-body temperature at Lao hugou valley No.12 glacier as polar continental glacier presents a higher trend.Meteorological and historical data indicate that the retreat and ablation of glaciers have been aggravated in recent years.Meanwhile,GPR combined with FDTD simulation provides good analytical tools for monitoring glacial variation along with climate change in our future.