Cation and sediment concentrations in basal ice from Oksfjordjokelen, North Norway

Basal ice samples were collected from ice exposures in a natural subglacial cavity beneath an outlet glacier of Oksfjordjokelen, North Norway. Sediment and cation (Ca2+, Mg2+, Na+, K+) concentrations were then determined, and indicate stacking of basal ice units producing a repeat pattern of 'clean firnification ice' overlying sediment-rich ice. All measured cations show correlation with sediment concentration indicating weathering reactions to be the dominant contributor of cations. Regressions of specific sediment surface area per unit volume with cation concentration are performed and used to predict cation concentrations. These predicted values provide an indication of cation relocation within the basal ice sequence. The results suggest limited melting and refreezing resulting in the relocation of predominantly monovalent cations downward through the profile. Exchange of cations into solution during the melting of sediment-rich ice samples has previously been suggested as a source of error in such investigations. Analyses of sediment-free regelation ice spicules formed at the bed show cation concentrations above firnification ice levels and comparable, in many instances, to the basal ice samples.