Characteristics of CryoSat-2 signals over multi-year and seasonal sea ice

CryoSat-2 Level 1B and Level 2 data are compared with coincident airborne laser scanner and airborne electromagnetic induction surveys conducted in the Baltic Sea in March 2011 and in the Lincoln Sea in March and April 2012. Across-track snagging caused range retrieval errors in all examined tracks. The L2 surface height profiles are very noisy due to poor retracker performance. Cryosat-2 L2 data are produced by tracking the strongest return in the Level 1B waveforms, not the first return. When a strong reflector is present off-nadir, the retracker incorrectly selects this surface as the surface location of the nadir point. The surface height profile is smoothed by tracking the first return point instead of the peak power return. Ice thickness data produced by retracking the CryoSat-2 L1B data showed good correlation with airborne electromagnetic induction measurements. CryoSat-2 and NASA Operation Ice Bridge data exhibited similar latitudinal freeboard gradients. Accurate measurements of sea ice freeboard or thickness changes can be achieved using appropriate spatial and temporal averaging.