Abstract
Using ground-penetrating radar (GPR), we measured and estimated the ice thickness of the Baishui River Glacier No. 1 of Yulong Snow Mountain. According to the position of the reflected media from the GPR image, combined with the radar waveform amplitude and polarity change information, the ice thickness and the changing medium position at the bottom of this temperate glacier were identified. Water paths were found in the measured ice, including ice caves and crevasses. A debris-rich ice layer was found at the bottom of the glacier, which produces strong abrasion and ploughing action at the bedrock surface. This results in the formation of different detrital layers stagnated at the ice-bedrock interface and numerous crevasses on the bedrock surface. Based on the obtained ice thickness and differential GPS data, combined with Landsat images, the kriging interpolation method was used to obtain grid data. The average ice thickness was 52.48 m and between 4740 and 4890 m above sea level, with a maximum depth of 92.83 m. The bedrock topography map of this area was drawn using digital elevation model from the Shuttle Radar Topography Mission. The central part of the glacier was characterized by small ice basins with distributed ice steps and ice ridges at the upper and lower parts.
Highlights
Ground penetrating radar (GPR) is a type of equipment that uses a continuous electromagnetic pulse to visualize shallow geological structures
The interpretation process of ice thickness and bedrock interface in the GPR image is illustrated by measuring point A of the transverse profile L1 (Figure 2a) as an example
The GPR image of profile L1 is shown as Figure 3a
Summary
Ground penetrating radar (GPR) is a type of equipment that uses a continuous electromagnetic pulse to visualize shallow geological structures. As there are different dielectric constants from different substances, the distribution or depth of the specific substance can be identified and analyzed according to the image from GPR, for instance, ice cavities, subglacial debris, and bedrock [1]. Due to the low attenuation rate and strong penetrability of GPR electromagnetic wave propagation in glacier medium, the GPR detection technology is widely used in the research area of ice thickness and subglacial terrains. Due to the higher ice temperature and water content as well as the high attenuation rate of the GPR electromagnetic signal in temperate glaciers, the penetrability in temperate ice can rapidly decrease. The higher the water content is, the stronger wave attenuation and scattering are. These problems increase the difficulty of GPR employed in temperate glaciers [16]. The reflection of electromagnetic waves from bedrock experiences interference and significantly influences the interpretation of GPR images [17]
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