Sea Ice Freeboard from Altika and Comparison with Cryosat-2 and Operation Icebridge

Abstract:

The algorithm for estimating sea ice freeboard from satellite radar altimetry is adapted and applied to Ka-band radar altimetry data from the French-Indian SARAL/AltiKa mission. This data is compared with contemporary state-of-the-art CryoSat-2 freeboard estimates for a full sea ice growth season in both the Arctic and Antarctic. We find that in both hemispheres, AltiKa consistently ranges higher than CryoSat-2, as would be intuitively expected for an altimeter operating at a higher frequency. The difference between the freeboard estimated by the two missions changes throughout the growth season, pointing to the role of the evolving snow layer on top of the sea ice floes. The data are also compared with Operation IceBridge airborne laser altimeter data from the 2013 and 2014 campaigns and it is found that AltiKa ranges much closer to the air-snow interface than CryoSat-2. AltiKa provides a new avenue of investigation for the issue of radar altimeter penetration into the snowpack on sea ice and could provide new insights for estimates of sea ice thickness, particularly in the Antarctic where Ku-band altimeters have typically performed badly.