Using Operation IceBridge to Link CryoSat-2 and ICESat-2 Sea Ice Freeboard Retrievals in the Antarctic

Despite recent advances in Arctic sea ice thickness retrievals from satellite altimetry, Antarctic sea ice thickness remains poorly constrained mainly due to uncertainties associated with the snow layer atop sea ice. The thick snow and complex stratigraphy can obscure the snow-ice interface in satellite-based Ku-band radar returns, hindering the retrieval of ice freeboard, snow depth, and thus sea ice thickness. Since 2009, Operation IceBridge has collected multi-instrument data over Antarctic sea ice primarily in the Weddell and Bellingshausen Seas. These high resolution data not only allow for the retrieval of the air-snow interface elevation, but also give better insight into the snow-ice interface elevation, along-track snow depth, and the potential for ice thickness.

In this presentation, we calculate Antarctic sea ice freeboard using Operation IceBridge data and discuss how it can be leveraged to assess sea ice retrievals from satellite altimetry missions, namely CryoSat-2 and ICESat-2. Freeboard is calculated using elevation data from the IceBridge Airborne Topographic Mapper (ATM) laser and the 13-17GHz Ku-band and 2-8GHz snow radars, as well as optical imagery from the Digital Mapping System (DMS). We utilize the elevation data and derived freeboard to validate a CryoSat-2 retrieval algorithm put forth in Fons and Kurtz (2019) that uses a waveform fitting technique to retrieve the air-snow interface elevation over Antarctic sea ice and calculate snow freeboard - effectively what is measured from laser altimeters such as ICESat-2. By reconciling the snow freeboard measurements from CryoSat-2 with those from ICESat-2, we aim to extend the time series of snow freeboard and move closer to improving sea ice thickness measurements in the Antarctic.