Sea-ice thickness assessments utilizing multi-frequency and variable coil-spacing electromagnetic induction (EMI) instruments were conducted in field trials at Barrow, Alaska, as part of the SIZONet (Seasonal Ice Zone Observation Network) April 2008 sea-ice field campaign. A 6.2 km shorefast ice transect along a Barrow community whaling camp trail was surveyed with three separate EMI instruments with coil spacings of 3.66, 2.00 and 1.22 m and at four operating frequencies ranging from 2 to10 kHz. Shorefast ice trails provide direct access for the local Iñupiat whaling community to reach the spring season ice edge or flaw lead, a polynya system that separates the oceanic ice pack from the coastal fast ice. The ice cover's anchoring strength and resistance to break-out events, factors important for ice safety, are directly related to the degree and extent of grounding of ice-shear ridges to the sea floor, thus providing the impetus to map ice thickness and deformation with EMI sounding techniques. For ice < ~4 m, point-scale thickness estimations along the whaling trail were similar for all EMI frequencies and coil spacings. However, for thicker ice, low frequency (2 and 5 kHz) EMI responses diverged from the higher frequency (9.8 and 10.0 kHz) responses, with maximum ice thicknesses of approximately 11 and 6 m, respectively, for an individual sounding. These results could not be explained by the simple half-space model of conductance used to construct instrument calibration curves, suggesting instead the possibility of grounded ridges – a distinctly different conductance model with sea ice underlain by ocean bottom sediments rather than sea water. This study presents an effort to evaluate the presence of grounded sea-ice ridges through forward and inversion modeling techniques applied to this rather unique EM dataset, with significant implications for expanded deployment of multiple-frequency EM.