Passive Microwave Remote Sensing of the Antarctic Ice Sheet: Retrieval of Firn Properties Near the Concordia Station

This letter discusses the retrieval of important thermal and physical properties of the Antarctic firn via spaceborne microwave radiometry focusing on the Concordia station. Previous studies have indicated that microwave radiometer measurements are sensitive to important properties of the firn from its surface down to deep isothermal ice. Expanding on those work, yearlong Advanced Microwave Scanning Radiometer 2 (AMSR2) and Special Sensor Microwave Imager/Sounder (SSMIS) radiometer measurements over the Concordia station have been used to create brightness temperature spectrograms, i.e., brightness temperatures versus month and frequency, and these spectrograms have been used to retrieve subsurface density and temperature properties of the firn using a plausible forward radiation model. It has been found that utilizing the wide microwave spectrum and long-term measurements, density variations due to internal firn layering, as well as seasonal temperature variations in the near-surface firn can be accurately estimated. In addition, densification of the firn with depth and the deep firn temperature can be retrieved with adequate ancillary data. The results mainly suggest that when deployed with other instruments, such as ground penetrating radars, wideband microwave radiometers can be useful for characterization of ice sheets in future polar remote sensing missions.