Permittivity of sea ice at Ka-Band

Measurements of the complex permittivity of sea ice at Ka-Band (26.5 to 40 GHz) were collected in the laboratory using a step frequency radar. Columnar and granular sea ice samples were prepared from cores of laboratory grown sea ice sheets with salinities ranging from 3 to 8 ppt. The authors measured the permittivity at temperatures from -30 to -12C in three orthogonal directions. They found, for all samples, that the imaginary part of the dielectric constant is highly dependent on the brine volume of the sea ice, which in turn depends on the bulk salinity and the temperature of the sample. For the columnar ice, consisting of approximately ellipsoidal brine pockets embedded in an ice matrix, they found that the imaginary part of the dielectric constant was anisotropic, and depended on the relative orientation of the electric field and the axes of the brine pockets. The highest values of the imaginary part of the permittivity were measured when the electric field was oriented parallel to the direction of ice growth, or along the longest axes of the brine pockets.