Polarisation of radio waves transmitted through Brunt Ice Shelf

The polarisation behaviour of radar waves transmitted through Brunt Ice Shelf at a site near Halley has been investigated using a step-frequency radar with a centre frequency of 300 MHz and a bandwidth of 150 MHz. Two linearly polarised aerials were used. At nine different orientations of the transmitting aerial, data were collected for nine different orientations of the receiving aerial, both covering a 180o rotation. This is the first study in which both phase and amplitude data have been analysed to determine the birefringence of the ice, which is related to the crystal fabric. The anisotropy in the effective permittivity is found to be about 0.14%, about a quarter of that found on Bach Ice Shelf with a 60 MHz radar in 1977.