Variability of surface density at Dotson Ice Shelf, West Antarctica

The ice mass balance of Antarctica has been steadily and strongly decreasing over recent decades, with major ramifications for global sea levels. Satellite remote sensing offers global, daily coverage of ice mass changes, which is essential for understanding land ice changes and their effects on global climate. However, we need to correct for processes including firn densification, glacial isostatic adjustment, elastic compensation of the Earth’s surface, ocean tides, and inverse barometer effect. Of these corrections, understanding the changes to the firn layer constitutes one of the largest uncertainties in making estimates of the surface mass balance from space. Furthermore, the development of firn models that aid our understanding of firn densification processes is hampered by a lack of observations.

Radar sounder reflections contain information about the roughness and permittivity of the reflecting interface, allowing us to map the spatial variability of the ice surface characteristics. In 2022, a helicopter-mounted ice-penetrating radar system developed by the University of Texas Institute for Geophysics collected high-quality radar observations over the Dotson Ice Shelf, West Antarctica. These surveys obtained clearly defined surface and bed reflections. We derived near-surface density along these survey flight lines using the radar statistical reconnaissance method developed by Grima, 2014. We calibrated our estimates with contemporary observations, including ground penetrating radar, a shallow ice core, an Autonomous phase-sensitive Radio Echo-sounder (ApRES), and radar soundings of well-defined surfaces from a calibration flight.