A comparison of Arctic sea ice freeboard products from Sentinel-3A and CryoSat-2 data

A number of satellite altimeters have been used to measure Arctic sea ice freeboard and to study its changes over the past decades (1992-present). In order to produce long-term time series of sea ice freeboard data set, it is essential to investigate the difference and consistency between different satellite-based sea ice freeboard data sets. Hence in this study, the comparison between ice freeboard products from altimeters on board Sentinel-3A and CryoSat-2 is constructed from February 2017 to January 2018 excluding summer months. The comparisons of echo waveform shapes and along-track radar freeboard estimates suggest that the freeboard difference between these two sensors is caused by the signal range bin number and the chosen retrackers for different surface types (leads and sea ice floes). Monthly gridded freeboard results show that mean values of two different satellite altimeters agree each other reasonably over the whole study period. In general, Sentinel-3A data set shows lower freeboard estimates than CryoSat-2 data set, this phenomenon is found in both First-Year ice (FYI) and Multi-Year ice (MYI) regions. No ice-type-related difference indicates the good consistency between Sentinel-3A and CryoSat-2 data sets. Over the whole period, mean freeboard estimates for the entire Arctic differs generally by not more than 0.07 m between Sentinel-3A and CryoSat-2. Compared to airborne Operation IceBridge (OIB) data, Sentinel-3A has closer sea ice freeboard estimates than CryoSat-2.