Airborne radar polarimetry over the Northeast Greenland Ice Stream

Ice streams are important export routes for ice from the interior of ice sheets to the ocean and a key component for projecting future sea level rise under continued climate heating. Over the last years, evidence emerged that the distribution of ice crystals in and near ice streams is highly anisotropic and strongly influences the viscosity of the ice. To map this crystal orientation fabric (COF) in space, radio-echo sounding has been proven as the most effective way. Several methods to deduce COF were applied to co-polarized airborne and ground-based radar data (i.e. all antennas have the same polarization direction) and tied to ice cores, with extensive coverage available around the EastGRIP ice core to analyse the COF within the Northeast Greenland Ice Stream (NEGIS). We extended this application to a new setup of cross-polarimetric surveys with AWI's ultrawideband airborne radar system and performed several surveys over NEGIS in 2022. 
Our presentation focuses on the results of this survey obtained from established methods to obtain the COF and compares them to ground-based results, such as from phase-sensitive radio-echo sounding (pRES) and a ground-based polarimetric radar system. We discuss the advantages of operating airborne radar systems in a cross-polarized mode in contrast to only co-polarized configurations to provide insights into fabric distribution on larger spatial scales as well as the disadvantages from a lower signal-to-noise ratio for imaging the bed as well as sounding internal layers.