Dielectric properties of sea ice at microwave frequencies

The dielectric properties of fresh water ice at microwave frequencies are reviewed. The properties of brine liquid were approximated by those of aqueous NaCl solutions. Various models for the shape and geometrical arrangement of brine pockets were used to obtain the dielectric properties of the mixture as a function of frequency, temperature, and salinity. The method can be applied at microwave frequencies when the length of brine inclusions is much smaller than the wavelength. The equations used for obtaining the properties of liquid brine are valid only at temperatures close to the freezing point of sea water. In Finland the temperature of ice is generally higher than -5 C so that the temperature range of calculations is adequate in most cases. The temperature dependence of the theoretical results agrees fairly well with the experimental values reported in literature. The model which assumes that brine pockets are elongated ellipsoids the orientation of which is random gives results that best agree with measurements.