First (Reflected) Light: GNSS Reflectometry on the McMurdo Ice Shelf

The ability to monitor glaciated surface types, including snow, ice and meltwater, at a high spatial resolution, is critical for monitoring overall glacier mass balance. Using an Antarctic ice shelf as a study site, the overall goal of this work is to test the feasibility of GNSS reflectometry (GNSS-R) in monitoring glacier surfaces. During the 2023-24 Antarctic austral summer, we conducted a data campaign to collect Global Navigation Satellite System reflectometry (GNSS-R) front-end samples from two 9-m towers sited on the McMurdo Ice Shelf near McMurdo Station, Antarctica. The tower near Phoenix airfield was surrounded by snow-covered ice. The tower near the former Pegasus airfield was a heterogeneous surface of bare ice and snow-covered ice. From mid-November to early December 2023, we collected GNSS-R, camera images, and lidar data of the ice shelf surface within a 20 m radius at each of these sites. From 2-m towers with a shared field of view offset 14 m horizontally from the 9-m towers, we also collected GNSS interferometric reflectometry (GNSS-IR) data using Earthscope commercially available geodetic antenna and receiver systems. All data were returned to the lab for post-processing. We show our first results from the site at Phoenix airfield, combining our GNSS-R estimates of surface reflectivity with the lidar and camera image data of the ice shelf surface. We find that the GNSS-R surface reflectivity is moderately positively correlated with the camera image mean red value for a snow-covered ice shelf surface. We also show GNSS-IR results from Phoenix for that day, for a satellite whose scattering zone overlaps with that of the GNSS-R zone. The reflector height estimates are robust, and lend credence to the reliability of the peak-to-noise ratio and spectral peak amplitudes. Preliminary results suggest that the spectral peak amplitude is comparable to that of the other glaciated surfaces.