摘要：We report impedance measurements of the complex dielectric permittivity ε = ε ′ − jε ″ of sea ice and laboratory-grown NaCl single crystals using 50 MHz Stevens Water Monitoring Systems Hydra Probes. Temperature cycling of the single-crystal samples shows hydrohalite precipitation, and hysteresis in ε ′ and ε ″ qualitatively consistent with the expected evolution of brine-inclusion microstructure. Measurements parallel and perpendicular to intra-crystalline brine layers show weak (<10%) anisotropy in ε ′ and a 20–40% difference in ε ″ due to enhanced d.c. conductivity along the layers. Measurements in landfast, first-year ice near Barrow, Alaska, USA, indicate brine motion in warming ice as the brine volume fraction v b increases above 5%. Plots of v b derived from salinity profiles against ε ′ and ε ″ for these and previous measurements display too much variability between datasets for unguided inversion of v b . Contributing to this variability are intrinsic microstructural dependence, uncertainties in v b , and sub-representative sample volumes. A standard model of sea-ice permittivity is inverted to derive the apparent brine-inclusion aspect ratio and bulk d.c. conductivity at a spatial scale complementary to previous measurements. We assess Hydra Probe performance in high-salinity environments and conclude that they are not generally suited for autonomous sea-ice salinity measurements, partly due to the range of relevant brine pocket inclusion length scales.
