Brine diffusion in first-year sea ice measured by Earthʹs field PGSE-NMR

Pulsed gradient spin echo (PGSE) measurements on first-year Antarctic sea ice have been performed using a portable Nuclear Magnetic Resonance probe that utilises the terrestrial magnetic field. This probe is a new device that incorporates independent transverse and longitudinal field gradient coils. A depth profile of the self-diffusion coefficient of liquid in brine inclusions has been measured through the 2002 season sea ice sheet in McMurdo Sound, near Cape Evans, Ross Island. The data is comprised of both horizontal and vertical brine diffusivity that have been measured in situ and with reduced invasive impact on the ice sheet, which constitutes a significant refinement of the Earthʹs field NMR technique. The observation that the depth dependence of the diffusion coefficient matched the expected magnitude with the temperature gradient through the ice sheet both confirmed the validity of our experiment and suggested that the sheet is best modelled as a matrix consisting of liquid inclusions in which the water molecules move in a Brownian manner.