Application of the Brewster angle to quantify the dielectric properties of ground ice formations

• 450 MHz GPR moveout surveys in endfire mode were conducted on a permafrost target.
• We saw a phase shift in the data when Tx was incident at the Brewster angle.
• With Brewster angle and Reflection coefficient relationship we derive permittivity.
• Brewster method derived permittivity values agree with in situ measurements.
• Method allows permittivity of unit underlying basal horizon to be derived.

Previous studies of ground ice using moveout type ground-penetrating radar (GPR) surveys indicate that the dielectric permittivity can constrain the type of ground ice present in the subsurface. Due to the high-loss nature of the active layer over permafrost targets, however, the signal strength of GPR signals is often insufficient to resolve the basal boundary required for determining the dielectric permittivity of an underlying unit. We apply a non-conventional antenna orientation and post-processing method to determine the dielectric permittivity of the unit underlying the lowest resolvable boundary. We conduct moveout surveys using a 450 MHz GPR with collinear parallel oriented antennas on two adjacent ground ice formations in the region of Thomas Lee Inlet, Devon Island, Nunavut. We exploit the Brewster angle to calculate the approximate dielectric permittivity of ground ice formations below the active layer. The results agree within 1 dielectric unit with on-ice permittivity measurements made during a complementary study of the site.