Arctic and Antarctic sea ice freeboard is derived from AltiKa altimetry data by adapting the processing method used to measure freeboard with the CryoSat-2 SIRAL instrument. AltiKa freeboard is compared with contemporary state-of-the-art CryoSat-2 sea ice freeboard data processed at University College London [1]. It is found that AltiKa consistently ranges higher than CryoSat-2, returning larger freeboard estimates. The offset in the Arctic is spatially homogenous but varies in magnitude over the course of a sea ice growth season. In the Antarctic the opposite is true - the offset is spatially variable and there is no strong seasonal signal. The satellite datasets are also compared against sea ice freeboard derived from Operation IceBridge airborne laser scanner data [2]. We find that AltiKa freeboard aligns more closely with the freeboard derived from the airborne laser scanner (i.e. the snow-air interface) compared to CryoSat-2, indicating that there is less penetration into the snow on sea ice at Ka-band than at Ku-band. We examine the usefulness of AltiKa for deriving sea ice thickness, in particular in the Antarctic where Ku-band satellite altimeters have typically had more difficulty [3,4]. AltiKa provides a highly complimentary dataset to Ku-band radar altimeters for sea ice studies and could provide useful insight into the problem of snow pack penetration in both the Arctic and Antarctic.

[1] S. W. Laxon et al, 2013, "CryoSat-2 estimates of Arctic ice thickness and volume", Geophysical Research Letters, Vol. 40, Issue 4, pages 732-737, doi: 10.1002/grl.50193.
[2] N. T. Kurtz et al, 2013, "Sea Ice Thickness, Freeboard, and Snow Depth Products from Operation IceBridge Airborne Data", The Cryosphere, 7:1035-1056, doi:10.5194/tc-7-1035-2013.
[3] N. T. Kurtz and T. Markus, 2012, "Satellite observations of Antarctic sea ice thickness and volume", Journal of Geophysical Research, 117, C08025, doi:10.1029/2012JC008141.
[4] K. A. Giles et al, 2008, "Antarctic sea ice elevation from satellite radar altimetry", Geophysical Research Letters, 35, L03503, doi:10.1029/2007GL031572.