Modeling of Anisotropic Electromagnetic Reflection from Sea Ice

• Main Authors: Golden,Kenneth M, Ackley,Stephen F
• Other Authors: COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
• Format: Text
• Language: English
• Published: 1980
• Subjects: Snow; Ice and Permafrost; Radiofrequency Wave Propagation; *RADAR REFLECTIONS; *SEA ICE; MATHEMATICAL MODELS; LAYERS; ANISOTROPY; BRINES; Ice; permafrost; Sea ice
• Online Access: http://www.dtic.mil/docs/citations/ADA094620; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA094620

The contribution of brine layers to observed reflective anisotropy of sea ice at 100 MHz is quantitatively assessed. The sea ice is considered to be a stratified, inhomogeneous, anisotropic dielectric consisting of pure ice containing ordered arrays of conducting inclusions (brine layers). Below the transition zone, the ice is assumed to have constant azimuthal c-axis orientation within the horizontal plane, so that the orientation of brine layers is uniform. The brine layers are also assumed to become increasingly well-defined with depth, since adjacent brine inclusions tend to fuse together with increasing temperature. A theoretical explanation for observed reflective anisotropy is proposed in terms of anisotropic electric flux penetration into the brine layers. Penetration anisotropy and brine layer geometry are linked to anisotropy in the complex dielectric constant of sea ice. In order to illustrate the above effects we present a numerical method of approximating the reflected power of a plane wave pulse incident on a slab of sea ice. Mixture dielectric constants are calculated for two polarizations of the incident wave: (1) the electric field parallel to the c-axis direction, and (2) the electric field perpendicular to the c-axis direction. These dielectric constants are then used to calculate power reflection coefficients for the two polarizations. Significant bottom reflection (R approximates 0.08) occurs when the polarization is parallel to the c-axis. However, when the polarization is perpendicular to the c-axis, the return may be almost completely extinguished (R less than 0.001). (Author)