Dispersion inversion of electromagnetic pulse propagation within freezing and thawing soil waveguides

Freeze and thaw processes are important components in characterizing glacial, periglacial and frozen ground environments, and hence the response of cryospheric regions to climate change. High‐frequency ground‐penetrating radar is particularly well suited for monitoring the freezing and thawing processes within the shallow subsurface (i.e., < 1 m depth) due to its non‐invasive nature and its sensitivity to the liquid water component in soil. The freezing of moist soil and thawing of frozen soil induce leaky and low‐velocity waveguides, respectively. Within these waveguide layers, the internally reflected radar energy produces interfering multiples that appear as a package of dispersed waves. Here, we present a new method for characterizing very shallow freeze and thaw processes, in which the waveguide properties are obtained by inverting the observed dispersion curves. This new method can non‐invasively monitor freezing and thawing processes in a wide range of glacial, periglacial and frozen ground studies.