Abstract:

Sea ice,as a component of the cryosphere,is very sensitive to the climate change.Study of sea ice physics needs accurate sea ice thickness data.This paper presents an electromagnetic-induction(EM) technique which can be used to measure the sea ice thickness distribution efficiently,and its successful application in Baltic Sea.Based on the electromagnetic field theory and by applying the electrical properties of sea ice and seawater,this technique can detect the distance between the EM instrument and the ice/water interface accurately,so the sea ice thickness can be obtained.Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at the same position allows a construction of the transformable formula of the apparent conductivity and sea ice thickness,and the verification of the sea ice thickness calculated by this formula indicates that electromagnetic-induction technique is able to measure sea ice thickness with good accuracy.The average relative error between EM measurements and drill holes data was 12%.The statistic of all ice thickness profiles shows the distribution of smooth surface ice in the Bay of Bothnian was 0.4—0.6 m.This result is in consistent with the EM-bird measurement.