Coastal sea level from inland CryoSat-2 interferometric SAR altimetry

The European Space Agency's CryoSat-2 satellite can operate in a novel synthetic aperture radar interferometric (SARIn) mode where its nominal footprint (swath) is observed by two antennas and the phase difference between the signals is used to determination the exact location of the scatterer through an off-nadir correction. The potential of SARIn for sea level determination is investigated over the fjords of Eastern Greenland. In principle the satellite should only track sea level within its nominal footprint of 7km across track, but we observe that scattering targets (fjords) within twice its nominal footprint are frequently observed but mislocated in CryoSat-2 due to phase wrapping. We devised a way to relocate the observations and correct the range accordingly. When CryoSat-2 is flying inland we consequently observed that the satellite occasionally provide valid sea level in fjords up to 13km away in the across-track direction. Key Points Sea level retrieved from CryoSat-2 SARIn when satellite flies 13km inland Phase unwrapping reveals hidden data in SARIn CryoSat-2 SARIn observe sea level in regions not previously covered by altimetry