GNGTS 2021 - Atti del 39° Convegno Nazionale

459 GNGTS 2021 S essione 3.2 After the interpretation of the ice-bedrock contact reflection along all GPR profiles, by picked data interpolation and gridding, we obtained bedrock maps (FIG. 3). The availability of more than 8.5 km-long GPR dataset covering all the glacier extension allowed to reconstruct in quite good detail the morphologies of the bedrock. With a mainly metamorphic composition, the bedrock extends from 3080 to 3280 m asl, with a mean slope of 25°. The slope ranges from 4° to 50°, being the steepest dips related to the lateral walls limiting the glacier toward North-East and South-West. A bedrock outcrop, noted on the GPR dataset and confirmed by orthophotos, corresponds to a rocky nunatak-like feature (yellow arrow in FIG. 3), on the NW side of the glacier. The morphology of the bedrock highlights a drainage systems, showing two major converging longitudinal incisions, extending along the entire length of the actual glacier area, equal to about 700 m, and joining close to the front. Smaller incisions coming down from the NE wall can be highlighted in the 3D reconstruction. The patterns of the main bedrock incisions seem to follow the general structural pattern of the area. As a matter of fact, an important tectonic lineament, that is still seismically active, characterizes this area and presumably constrained the evolution of the trough in which the glacier is flowing down. The detailed reconstruction of the bedrock morphology allowed to calculate the ice volume of the glacier: in 2020 it had an extension of 218130 m 2 and a volume of 5451140 m 3 , the glacier has a mean ice thickness of 25 m. If we take into account the presence of the high scattered zone, the volume of electro-magnetically transparent ice reduces to 3291770 m 3 . Fig. 2 - GPR attributes analysis: (A) Amplitude display of a GPR profile after processing, (B) First Derivative, (C) Envelope, (D) Sweetness, (E) Variance, (F) Dominant Frequency, (G) Cosine of phase. Black solid line marks the ice-bedrock contact detection; where it remains hidden, the black line converts to dots.