It is critical for climate, water resources, ecology, and engineering construction in China to accurately assess the three-dimensional distribution and periodic change of permafrost. Permafrost is mainly distributed in high-elevation regions in China. Therefore, the surface geophysical prospecting suffers from low efficiency, high cost, and poor transportation in determining the thickness of permafrost in China. In contrast, the airborne electromagnetic methods using resistivity difference enjoy great advantages. This study established a geoelectric model based on the thickness and resistivity of permafrost in Qilian area, Qinghai Province. Then, by simulating the thickness and resistivity of permafrost, low resistance layer under permafrost, flight height, and changes in the angles of receiver coils, this study analyzed the differences in electromagnetic responses under different conditions obtained from one-dimensional forward modeling using time-domain and frequency-domain airborne electromagnetic systems AeroTEM and Impulse. Based on this, this study assessed the capability of airborne electromagnetic methods to detect the top and bottom interfaces of permafrost. According to the simulation results, frequency-domain airborne electromagnetic system Impulse can determine the top interface of the permafrost covered by a marsh, wetland, or moist meadow according to the thickness of melted permafrost under a low noise level. In comparison, time-domain airborne electromagnetic system AeroTEM can determine the bottom interface of the permafrost, with the determination accuracy significantly improving when low-resistivity layers occur beneath the permafrost. Therefore, the top and bottom interfaces of permafrost can be jointly determined using frequency and time-domain airborne electromagnetic data. The results of this study will provide theoretical support for the future application of airborne electromagnetic methods to permafrost surveys in China.
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