Monitoring the seasonal changes of an englacial conduit network using repeated ground penetrating radar measurements

Abstract. Between 2012 and 2019, repeated 25 MHz ground penetrating radar (GPR) surveys were carried out over an active englacial conduit network within the ablation area of the temperate Rhonegletscher, Switzerland. In 2018 and 2019 the repetition survey rate was increased to monitor seasonal variations. The resulting GPR data were processed using an impedance inversion workflow to compute GPR reflection coefficients and layer impedances, which are indicative of the conduit's infill material. The spatial and temporal evolution of the reflection coefficients also provided insights into the morphology of the Rhonegletscher's englacial conduit network. During the summer melt seasons, we observed an active, water-filled, sediment transporting englacial conduit network that yielded large negative GPR reflection coefficients (