2-DIMENSIONAL MAPPING OF SEA-ICE KEELS WITH AIRBORNE ELECTROMAGNETICS

Airborne electromagnetic (AEM) equipment can be used to sense sea ice thickness by interpreting the AEM data to obtain the distance from the towed bird that holds the EM system to the ice/seawater interface. The ice thickness itself is obtained by subtracting from that quantity the distance from the bird to the upper ice surface, as determined by a laser altimeter. By compiling numerical-model results, we constructed an interpretation chart that relates the parameters of the observed AEM response anomaly to the geometric variables of the ice keel. The strike length of the ice keel should be about three times the bird height above the ice-water interface, so that the assumption of two-dimensionality holds. The use of the chart has been verified by interpreting field AEM data. -from Authors