Alpine ice cores and ground penetrating radar: combined investigations for glaciological and climatic interpretations of a cold Alpine ice body

Abstract

Accurate interpretation of ice cores as climate archives requires detailed knowledge of their past and present geophysical environment. Different techniques facilitate the determination and reconstruction of glaciological settings surrounding the drilling location. During the ALPCLIM 1 project, two ice cores containing long-term climate information were retrieved from Colle Gnifetti, Swiss-Italian Alps. Here, we investigate the potential of ground penetrating radar (GPR) surveys, in conjuction with ice core data, to obtain information about the internal structure of the cold Alpine ice body to improve climatic interpretations. Three drill sites are connected by GPR profiles, running parallel and perpendicular to the flow line, thus yielding a three-dimensional picture of the subsurface and enabling the tracking of internal reflection horizons between the locations. As the observed reflections are of isochronic origin, they permit the transfer of age-depth relations between the ice cores. The accuracy of the GPR results is estimated by comparison of transferred timescales with original core datings, independent information from an older ice core, and, based on glaciological surface data, findings from flow modeling. Our study demonstrates that GPR is a mandatory tool for Alpine ice core studies, as it permits mapping of major transitions in physical-chemical properties, transfer of age-depth relations between sites, correlate signals in core records for interpretation, and establish a detailed picture of the flow regime surrounding the climate archive.

Deriving micro- to macro-scale seismic velocities from ice-core <i>c</i> axis orientations

“…Equally, our results can provide context for data collected with frozen-in seismometers in boreholes, where evidence for shear-wave splitting on nonvertical ray paths was found (David Prior, personal communication, 2018). Lastly, we want to highlight that, while the depth scale of the KCC ice core differs from that of the EDML ice core by a factor of 1/35, the presented case study is another example (Eisen et al, 2003;Diez et al, 2014) of the importance of midlatitude high-altitude glaciers for in situ laboratories to study fundamental processes in glaciers.…”

To what extent do water isotope records from low accumulation Alpine ice cores reproduce instrumental temperature series?

“…Haeberli et al (1988); Lu¨thi and Funk (2000); Eisen et al (2003) for geometry and glacier flow, Hoelzle et al (2011) for the englacial temperature and Alean et al (1983) concerning the surface accumulation pattern. Here, we present only a brief overview relevant for assessing the significance of water isotope records.…”

“…Since both glacio-meteorological parameters depend mainly on the slope (aspect) of the saddle surface, there is a systematic accumulation rate increase towards the central saddle point. This is inferred from various stake readings (Alean et al, 1983;Lu¨thi and Funk, 2000) and ground-penetrating radar (Eisen et al, 2003;Konrad et al, 2013) showing that net accumulation rates roughly double from the near bergschrund area down towards the saddle point. The mean d…”

Supercooled interfacial water in fine-grained soils probed by dielectric spectroscopy

“…the MARSIS and SHARAD projects, Picardi et al, 2004;Seu et al, 2007), in cryospheric applications (e.g. Eisen et al, 2003Eisen et al, , 2006 and in studies of permafrost soils (e.g. Wollschläger et al, 2010).…”