On the use of electromagnetic induction sounding to determine winter and spring sea ice thickness in the Antarctic

The suitability of using a portable electromagnetic induction (EMI) sounding device for determining sea ice thickness under winter and spring conditions in the Antarctic is evaluated. Ice thickness estimates from the instrument are compared with drilled measurements along a series of transects on East Antarctic pack ice and fast ice. The data indicate that the instrument estimates the undeformed sea ice thickness to within 10% of drilled thickness measurements; however, thickness estimates over deformed ice show much larger deviations. Sea ice conductivity profiles along each transect were calculated using ice core salinity data and ice-snow interface temperatures. The analysis indicates that first-year Antarctic sea ice generally has a higher conductivity (35-75 mS m-1) than reported for Arctic sea ice. However, this does not adversely affect the EMI sounding technique for determining sea ice thickness as this conductivity is still significantly less than for seawater, and the ice effectively remains transparent to the EM field. The EMI instrument used in this experiment was fitted with an ice thickness processing module (PM) which provided accurate estimates of sea ice thickness once correctly calibrated. The results from these preliminary experiments over winter and spring Antarctic sea ice indicate that EMI sounding has great potential to provide thickness data over the undeformed component of the Antarctic pack ice at this time of year.