Electromagnetic-induction (EM) sounding is the main took of the Sea Ice Physics group to measure the thickness of sea ice in the Arctic and Antarctic. EM ice thickness measurements are based on the contrast of electrical conductivity between sea water and sea ice to determine the distance of the EM instrument to the ice-water interface. The method can be applied with ground-based and airborne sensors.
Ground-based EM surveys usually include hand-held sensors that are pulled on a sledge across the ice. Airborne EM (AEM) systems include custom-built instruments that are towed 12 to 20 meters above the ice surface using helicopters from land or from RV Polarstern. Since 2009, AEM measurements are also conducted with the research aircraft Polar 5 operating from different Arctic Research Stations, such as the Danish Station Nord in nord-east Greenland or Station Alert, in Canada. The fixed-wing based flight pattern follow straight lines of several hundreds of kilometers, while helicopter flights are typically performed along a triangular track with a side length of 40 to 80 km.
More information on the method can be found on meereisportal.de