Chemical evidence in polar ice cores from dielectric profiling

The dielectric stratigraphy of a 130 m ice core from Dolleman Island, Antarctic Peninsula, shows large variations in the dielectric relaxation process and in conductivity. A comparison with the chemical stratigraphy of the core demonstrates the decisive role played by both acids and salts in determining the electrical behaviour of natural ice. The dielectric response is sensitive both to the type of impurity and to its distribution within the ice fabric. The evidence supports other observations of the localization of sulphuric acid at three-grain boundaries: in contrast, the salt impurity appears to be largely incorporated into the ice lattice. The overriding importance of the dielectric profiling technique is that it is the only profiling tool so far developed that is sensitive to the presence of salt in polar ice cores.