Layer-optimized SAR processing with a mobile pRES to illuminate the internal layering of an alpine glacier

The internal, isochronous layering of glaciers is shaped by accumulation and ice deformation. Information about these processes can be inferred from observing the layers using radar sounding. The reflectivity of the layers depends on density (permittivity) and acidity (conductivity) contrasts which tend to decrease with depth. At places like alpine glaciers where logistic limitations often only allow the deployment of lightweight and power-constrained ground-penetrating radar systems, it can therefore be challenging to illuminate the deeper radio-stratigraphy.

The phase-sensitive Radio Echo Sounder (pRES) is a lightweight frequency modulated continuous wave radar which allows the use of coherent Synthetic Aperture Radar (SAR) processing techniques to improve the signal-to-noise ratio of internal reflection horizons. Using a mobile pRES we collected a radar profile on an alpine glacier (Colle Gnifetti, Italy/Switzerland). Here, we demonstrate how to apply layer-optimized SAR techniques to make deep internal layers visible, which could not be seen by a conventional pulsed radar. We evaluate the requirements on spatial resolution and positioning accuracy during data acquisition, necessary for applying layer-optimized SAR processing, as they constrain the feasibility of the method. We further discuss implications on how density and acidity contribute to decreasing dielectric contrasts.