GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 Results As first, we compared the GPR amplitude section shown as (Fig. 1a) in Delf et al., 2022 with the same data (Fig 1b) except from the topographic correction which was not possible due to the lack of availability of such an information. Minor differences in the interpretation of the bedrock (Fig 1 orange points) and of the limit between cold and warm ice have been highlighted. With the integrated attribute analyses we imaged an anomalous zone just above the Cold/Temperate-ice Transition Zone (CTZ) boundary in the cold ice region not visible in the amplitude GPR section (Fig. 1 and Fig. 2). It is interesting that such anomalous zone is not present on the entire section but only in the central part of the glacier, where the maximum ice thickness is present. The anomalous zone has peculiar characteristic quite different from all the other glaciological facies. Fig. 1 - GPR longitudinal profile of Von Postbreen polythermal glacier. a) the data from Delf et al 2022 (Figure 1a therein); b) the same GPR amplitude data with our interpretation; c) dominant frequency attribute; d) phase attribute. The colored points mark the same positions in the different profiles. Interpreted horizons colors refer to the interpretation provided by Delf et al., 2022, while the top of the anomalous zone found in our analysis is marked by the yellow horizon, WI: warm ice; CI: cold ice; CTZ: Cold/temperate-ice Transition Zone. In particular, phase attribute marks not continuous characteristics while the frequency is somehow variable and overall lower than the warm ice just below (Fig. 1c and d and Fig. 2b and d). In addition, the sweetness attribute condenses the information highlighting that the anomalous zone is characterized by low overall sweetness which is from one side higher and different from the zone just above it, and from the other lower that the warm ice facies just below it.