Interpretation of radar returns from sea ice

The heterogeneous nature of the sea ice surface with respect to topography and reflectivity characteristics poses serious problems in interpreting radar returns to the precision needed for modern transportation over the polar ice pack. The physical properties of sea ice are discussed. A swept frequency technique is used to determine the electromagnetic properties of
3.5\permil
salinity sea ice in the frequency band from 26.5 to 40.0 GHz. Lack of influence by liquid brine is noted in the real part of the complex permittivity at temperatures below
-7\deg
C; a marked change in dielectric loss is noted with change in the orientation of the liquid brine inclusions in sea ice with respect to the millimeter wave electric field