In-situ measurements on the conductivity and surface impedance of sea ice at VLF


  • Duncan McNeill,

  • Pieter Hoekstra


An experimental program to measure in-situ values of the electrical resistivity and surface impedance of sea ice at VLF was carried out at Point Barrow, Alaska. Temperature, salinity, and resistivity were measured as a function of depth in the ice for both first-year and multiyear sea ice by means of cored samples. All three quantities varied with the age of the ice, and, in addition, the resistivity varied with age from 102 ohm m to 104 ohm m at the surface and in general down to a few ohm m at the sea-water interface.

The wavetilt of a VLF plane wave propagating over sea ice is theoretically linearly dependent on the thickness. Measurements of the quadrature phase wavetilt at 18.6 kHz give values that are of the right order of magnitude but erratic in local behavior. Short-spacing Wenner array resistivity measurements and telluric current measurements at VLF demonstrated that the erratic behavior was due to significant horizontal variations of the sea-ice resistivity over distances of a few m.