High-resolution helicopter-borne ground penetrating radar survey to determine glacier base topography and the outlook of a proglacial lake

We present imaging results from a high-density helicopter-borne ground penetrating radar (GPR) survey and several ground-based GPR profiles over the Rhone glacier, in Valais, Switzerland. Basal topography and ice thicknesses (maximum 173.7 m ± 10.2 m within survey area) are derived and interpreted providing an insight into the proglacial lake development. Expected continued retreat of the Rhone glacier reveals the tripling of the potential proglacial lake volume from 1.3 million cubic meters to 4.5 million cubic meters. Qualitative analysis of the surface-based GPR over several seasons (2012-2017) highlights the temporal basal and englacial reflectivity variation. Potential englacial water pockets or conduits cause strong englacial reflections located within an overdeepen feature, observed only on the recent 2017 GPR data.