Comparison of measurements from different radio-echo sounding systems and synchronization with the ice core at Dome C, Antarctica

Abstract

Abstract. We present a compilation of radio-echo sounding (RES) measurements of five radar systems (AWI, BAS, CReSIS, INGV and UTIG) around the EPICA Dome C (EDC) drill site, East Antarctica. The aim of our study is to investigate the differences of the various systems in their resolution of internal reflection horizons (IRHs) and bed topography, penetration depth and capacity of imaging the basal layer. We address the questions of the compatibility of existing radar data for common interpretation and the suitability of the individual systems for reconnaissance surveys. We find that the most distinct IRHs and IRH patterns can be identified and transferred between most data sets. Considerable differences between the RES systems exist in range resolution and depiction of the bottom-most region. Considering both aspects, which we judge as crucial factors in the search for old ice, the CReSIS and the UTIG systems are the most suitable ones. In addition to the RES data set comparison we calculate a synthetic radar trace from EDC density and conductivity profiles. We identify 10 common IRHs in the measured RES data and the synthetic trace. We then conduct a sensitivity study for which we remove certain peaks from the input conductivity profile. As a result the respective reflections disappear from the modeled radar trace. In this way, we establish a depth conversion of the measured travel times of the IRHs. Furthermore, we use these sensitivity studies to investigate the cause of observed reflections. The identified IRHs are assigned ages from the EDC's timescale. Due to the isochronous character of these conductivity-caused IRHs, they are a means to extend the Dome C age structure by tracing the IRHs along the RES profiles.

Englacial Architecture and Age‐Depth Constraints Across the West Antarctic Ice Sheet

“…IPR is the primary method by which ice thickness has been measured across Antarctica (e.g., Fretwell et al, 2013). However, most IPR surveys have also sounded numerous englacial internal reflection horizons (IRHs) throughout the ice column (e.g., Steinhage et al, 2001;Winter et al, 2017), and these, away from density-driven reflectivity contrasts in the near-surface (Kovacs et al, 1995), and the strained ice of the basal zone where anisotropic effects become important (Fujita et al, 2000;Wang et al, 2018), are widely attributed to conductivity variations associated with the atmospheric deposition of impurities at the surface Holschuh et al, 2018;Miners et al, 2002). With the exception of basal ice and erosional surfaces (e.g., Arcone et al, 2012;Cavitte et al, 2016;Holschuh et al, 2018), continuous IRHs can be considered isochronal and hence reflect the advection of paleo-ice surfaces.…”

High-resolution boundary conditions of an old ice target near Dome C, Antarctica

“…The surface time delay is subtracted from the bed time delay to obtain the two way travel time in the ice column and, using an appropriate refractive index for ice ( √ 3.15), we convert to ice thickness. We choose not to apply a firn correction to ice thicknesses; as shown in Peters et al (2007), a firn correction is not required for our focusing, and will not affect the conclusions in this paper (firn correction is however critical for isochrone interpretation Cavitte et al, 2016;Winter et al, 2017). Bed elevations are derived by subtracting the ice thickness from concurrently collected laser or radar altimetry; all elevations are referenced to the WGS-84 ellipsoid.…”

Is there 1.5-million-year-old ice near Dome C, Antarctica?

“…1), which are all related to the EDC ice core. These data resolve the bed and internal isochrones and are suitable for the oldest-ice search (Winter et al, 2017). The isochrones are dated up to about 366 kyr BP using the most recent AICC2012 chronology established for the EDC ice core Veres et al, 2013).…”