Calibration of a Low Induction Number Electromagnetic Instrument for Sea Ice Thickness Measurements

Sea ice thickness measurements using low induction number electromagnetic instruments require accurate electromagnetic data. Calibration of EM sea ice thickness data acquired using a shipbome low induction number electromagnetic sensor can be performed by making measurements at a range of heights over level sea ice of known thickness, and by comparing the observed data with the expected layered-earth response. Calibration corrections can be derived using least-squares inversion to minimise the misfit between the observed data and the theoretical response, and can be applied to ship-borne sea ice thickness data during post-processing. This paper presents a case history illustrating identification and correction of calibration errors in low induction number electromagnetic data for shipborne Antarctic sea ice thickness measurements. The method described could also be applied to calibration of low induction number electromagnetic instruments for conventional environmental and engineering geophysical surveys.