Electromagnetic–induction (EM) instruments can be used to estimate sea-ice thickness because of the large contrast in the conductivities of sea ice and sea water, and are currently used in investigations of sea-ice thickness. In this study we analyze several snow, ice and sea-water samples and attempt to derive an appropriate formula to transform the apparent conductivity obtained from EM measurements to the total thickness of snow and ice for all regions and seasons. This was done to simplify the EM tuning procedure. Surface EM measurement transects with the instrument at varying heights above the ice were made in the Chukchi Sea, off East Antarctica, in the Sea of Okhotsk and in Saroma-ko (lagoon). A standardized transformation formula based on a one-dimensional multi-layer model was developed that also considers the effects of water-filled gaps between deformed ice, a saline snow slush layer, and the increase in the footprint size caused by increasing the instrument height. The overall average error in ice thickness determined with the standardized transform was <7%, and the regional average errors were 2.2% for the Arctic, 7.0% for the Antarctic, 6.5% for the Sea of Okhotsk and 4.4% for Saroma-ko.
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