Priska Andrea Hunkeler

• Characterization of the sea-ice cover is of great importance for understanding processes and feedback mechanisms and predicting the evolution of the polar-climate system. One important climate relevant parameter, which can be used for this characterization, is sea-ice thickness. It can be retrieved by a variety of methods, where the majority is based on indirect determination from related parameters such as sea-ice draft or freeboard. A direct method that can be applied on the ground or from airborne platforms is electromagnetic (EM) induction sounding. In this thesis, the potential of EM sensors with multiple frequencies was investigated in designated case studies for the retrieval of sea-ice thickness, but also for the porosity of sea ice. A unique EM dataset over fast ice at Atka Bay, Antarctica was analyzed with a laterally-constrained Marquardt-Levenberg inversion. The results provide evidence that in addition to sea-ice, also platelet-layer thickness retrieval is possible using a non-destructive method, a finding which is expected to significantly facilitate its volume estimation in the future. The developed methodology is a crucial step in determining the relative contribution of sub-ice shelf processes to sea-ice mass balance in the Southern Ocean, and hence a valuable tool to better understand ocean/ice-shelf interaction.