Dielectric Behaviour of Firn and Ice from the Antarctic Peninsula, Antarctica

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Abstract
Dielectric experiments have been undertaken at temperatures between −2° and −70° C in the frequency range 10Hz to 100 kHz on 14 firn and ice samples retrieved from the Antarctic Peninsula. This investigation shows that the dielectric behaviour of polar samples from the Antarctic Peninsula is very similar to that of polar firn and ice from Greenland and from elsewhere in Antarctica. In contrast, temperate samples from the Antarctic Peninsula have relaxation times up to ten times shorter for a given temperature between –20° and –70°C, and have higher values of high-frequency conductivity than those of polar samples. Consequently, the thermal regime (temperate or polar) can be distinguished by the dielectric behaviour of the samples. High-frequency conductivities of polycrystalline samples from the Antarctic Peninsula match the trends of published conductivity data for HF- and HCl-doped laboratory ice; higher conductivities are associated with coastal sites where greater concentrations of marine ions occur in snow. Annealing polar firn above −10°C results in elevated conductivities across all frequencies measured and shortened relaxation times. Thus, samples for dielectric analysis should not be warmed to above –10°C for risk of irreversibly altering their dielectric behaviour.