Geophysical signature of a World War I tunnel-like anomaly in the Forni Glacier (Punta Linke, Italian Alps)

Abstract

Global warming and the associated glacier retreat recently revealed the entrance to an ice–rock tunnel, at an altitude of ~3600 m a.s.l., in the uppermost portion of the Forni Glacier in the Central Italian Alps. The tunnel served as an entrance to an Austro-Hungarian cableway station excavated in the rocks during the Great War just behind the frontline. A comprehensive geophysical survey, based on seismic and ground-penetrating radar profiling, was then undertaken to map other possible World War I (WWI) remains still embedded in the ice. The ice–rock interface was reconstructed over the entire saddle and in the uppermost portion of the glacier. A prominent linear reflector was surprisingly similar to the common response of buried pipes. The reflector orientation, almost longitudinal to the slope, does not seem to be compatible with a glacial conduit or with other natural features. Numerical simulations of a series of possible targets constrained interpretation to a partly water-filled rounded shape cavity. The presence of a preserved WWI tunnel connecting Mount Vioz and Punta Linke could be considered a realistic hypothesis. The Forni glacier could be still considered polythermal and comprised of cold ice without basal sliding in its top portion.

Active Layer and Permafrost Investigations Using Geophysical and Geocryological Methods—A Case Study of the Khanovey Area, Near Vorkuta, in the NE European Russian Arctic

“…The degree of freezing of interstitial water has a negligible effect on density and magnetic permeability, precluding the use of gravimetric and magnetic techniques. It is fortunate that freezing has a marked effect on dielectric permittivity (Thomson et al, 2012), conductivity (Palacky, 1988;Seppi et al, 2015;Picotti et al, 2017;Francese et al, 2019), and seismic wave velocities (Carcione and Seriani, 1998). Hence, geoelectric, electromagnetic, and seismic methods constitute the best approaches to quantify the thawing degree of ice in sediments.…”

“…Geophysical surveys, as ground-penetrating radar (GPR) and electrical resistivity tomography (ERT), have been extensively used to study active layer and permafrost features. However, although the GPR technique performs well only for low clay contents in the subsoil (e.g., Arcone and Delaney, 1982;Palacky, 1988;Delaney et al, 1990;Doolittle et al, 1990;Arcone et al, 1998;Hinkel et al, 2001), the ERT method enables the characterization of both the active layer and the underlying permafrost for almost all soil textures (e.g., Kasprzak, 2015;Seppi et al, 2015;Kasprzak et al, 2017;Léger et al, 2017;Picotti et al, 2017;Francese et al, 2019;Farzamian et al, 2020;Isaev et al, 2020). In addition, electromagnetic induction methods have been successfully used to estimate the thickness of permafrost (e.g., Isaev et al, 2020).…”