The relationship between the ground surface layer permittivity and active-layer thawing depth in a Qinghai-Tibetan Plateau permafrost area

•Underlying surface and climate condition control the active layer thawing process.•Soil moisture and biomass determine the ground surface layer permittivity.•A simple active layer thickness distribution forecasting formula was recommended.

Active-layer thickness's distribution is a key parameter for permafrost area studies. In the past, the factors of vegetation, soil water content usually were employed to forecast the spatial distribution of active-layer thickness. But in coarse material distribution area, the above method is often unsatisfactory due to the failure in accurate acquisition of biomass and soil water content. In this paper, a simple method was recommended to be used for calculating of active layer thickness distribution, which is suitable for all kinds of soil texture.Our study analyzed the relationship between ground surface layer permittivity and the thawing depth of the active layer in a permafrost area that was undisturbed by subsurface water flow or local melting. Ground surface layer permittivity is confirmed as having a strong correlation with soil moisture content and biomass of the vegetation cover. We used the direct ground wave velocities from GPR detecting results to compute the dielectric permittivity. Our conclusion is that in our specific study area, a power function relationship existed between the ground surface layer permittivity and the thawing depth of the active layer.