Earth's field NMR in Antarctica: A pulsed gradient spin echo NMR study of restricted diffusion in sea ice

We report on the use in Antarctica of a nuclear magnetic resonance spectrometer which utilizes the terrestrial magnetic field. Free induction decay data are used to obtain estimates of brine content, in samples of sea ice extracted from the annual ice of McMurdo Sound, in the vicinity of Cape Evans, Ross Island. pulsed gradient spin echo experiments were performed on these samples in which the orientation of the gradient with respect to the ice growth axis was varied and the separation time between the gradient pulses was varied. Anisotropic restricted diffusion effects are apparent; and we use these to tentatively model the brine pocket morphology. (C) 1998 Academic Press.