Response to reviews on "High resolution boundary conditions of an old ice target near Dome C, Antarctica"

Abstract

A high-resolution (1 km line spacing) aerogeophysical survey was conducted over a region near the East Antarctic Ice Sheet's Dome C that may hold a 1.5 Myr climate record. We combined new ice thickness data derived from an airborne coherent radar sounder with unpublished data that was in part unavailable for earlier compilations, and we were able to remove older data with high positional uncertainties. We generated a revised high-resolution digital elevation model (DEM) to investigate the potential for an old ice record in this region, and used laser altimetry to confirm a Cryosat-2 derived DEM for inferring the glaciological state of the candidate area. By measuring the specularity content of the bed, we were able to find an additional 50 subglacial lakes near the candidate site, and by Doppler focusing the radar data, we were able to map out the roughness of the bed at length scales of hundreds of meters.We find that the primary candidate region contains elevated rough topography interspersed with scattered subglacial lakes and some regions of smoother bed. Free subglacial water appears to be restricted from bed overlain by ice thicknesses of less than 3000 m. A site near the ice divide was selected for further investigation. The high resolution of this ice thickness data set also allows us to explore the nature of ice thickness uncertainties in the context of radar geometry and processing.

Age stratigraphy in the East Antarctic Ice Sheet inferred from radio-echo sounding horizons

“…Furthermore, mapping of radar-detected horizons increases confidence that layering at those depths is undisturbed and facilitates age extrapolation of the maximum expected age at the coring location Parrenin et al, 2017). These uses of stratigraphic information for future drill-site selection are strongly exploited in the currently running reconnaissance studies for the International Partnership in Ice Core Sciences (IPICS) Oldest Ice target, aiming at the retrieval of a continuous 1.5 Myr old ice-core record (Brook et al, 2006;Karlsson et al, 2018;Parrenin et al, 2017;Van Liefferinge and Pattyn, 2013;Van Liefferinge et al, 2018;Young et al, 2017).…”