Sea salt dependent electrical conduction in polar ice
A 45 m length of ice core from Dolleman Island, Antarctic Peninsula has been dielectrically analysed at 5 cm resolution using the dielectric profiling (DEP) technique. The core has also been chemically analysed for major ionic impurities. A statistical analysis of the measurements shows that the LF (low frequency) conductivity is determined both by neutral salt and acid concentrations. The statistical relationships have been compared with results from laboratory experiments on ice doped with HF (hydrogen fluoride). Salts (probably dispersed throughout the ice fabric) determine the dielectric conductivity. The salt conduction mechanism is probably due to Bjerrum L defects alone, created by the incorporation of chloride ions in the lattice. Samples of ice from beneath the Filchner-Ronne Ice Shelf were also measured and display a similar conduction mechanism below a solubility limit of about 400 μM of chloride. The temperature dependence of the neutral salt, acid and pure ice contributions to the LF conductivity of natural ice between −70°C and 0°C is discussed. These results allow a comprehensive comparison of dielectric and chemical data from natural ice.