GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 3.2 ___ GNGTS 2023 Fig. 2 - Close up of a portion of the longitudinal GPR section of Von Postbreen polythermal glacier (see Fig. 1a for positioning) where there is a local uplift of the bedrock. a) amplitude data; b) dominant frequency attribute; c) phase attribute; d) sweetness attribute. The top of the anomalous zone is marked by continuous yellow horizon, CTZ: Cold/temperate-ice Transition Zone, WI: warm ice, CI: cold ice. In Fig 3 we plot a close up over the terminal part of Von Postbreen glacier: In this zone we note the lack of the anomalous zone above the CTZ in the cold ice transparent EM zone. On the other hand, the cold/warm ice zone are characterized in terms of high frequency values for the cold ice (CI) and a variable frequency pattern for the warm ice (WI). Something similar occurs for the sweetness but with inverted values as compared to frequency attributes. The phase attribute is diagnostic for the correct and precise location of the different horizons (Fig 1d, 2d, 3d) between the various EM facies and depicts the anomalous zone (Fig 2d) as a quite chaotic facies with rapid local phase variations, while just above it exhibit a more continuous trend partially related to some coherent residual noise in the data.