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

Abstract

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 We combined new ice thickness data derived from an airborne coherent radar sounder with unpublished data that was in part unavailable for earlier compilations, and we were able to remove older data with high positional uncertainties.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.

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

“…Basal melting is of course negligible at these two oldest-ice spots. Melting is, however, significant around EDC (which is consistent with known basal melting at this place), on the other side of LDC and on the bed ridge adjacent to the Concordia Subglacial Trench (called here the Concordia Ridge), consistent with the observation of subglacial lakes (Wright and Siegert, 2012;Young et al, 2017). While it is surprising that basal melting is so large across the ridge of the bed, where the ice thickness is smaller, the 1-D assumption is probably invalid in this region, since the ice has been significantly advected horizontally over regions with very different basal conditions (i.e.…”

Accumulation patterns around Dome C, East Antarctica, in the last 73 kyr

“…Even though the absolute magnitudes of slope and curvature changes we observe are relatively small (on the or-der of 10 −3 and 10 −7 m −1 , respectively), other studies have shown that even very small slope changes can have a strong influence on wind-borne redistribution of snow (Grima et al, 2014;King et al, 2004;Whillans, 1975). However, a single mechanism has yet to be described that would explain the relationship between CPWD (and therefore SPWD) and small-scale accumulation variations.…”

“…King et al (2004) show that local slope changes of 0.01 can create up to 30 % variations in accumulation, and invoke a highly non-linear relationship between wind speed and snow transport to explain the type of accumulation variability they observe. Whillans (1975) also shows that slope changes as small as 0.001 over a distance of 3 km can affect snow deposition, and argues for a relationship between slope, wind strength and mass drift transport.…”

“…Black and Budd (1964) and Budd (1971) were the first to observe the close relationship between bedrock relief, surface slope and accumulation rates in Wilkes Land. Whillans (1975) details how wind speed and direction can affect total mass balance in Marie Byrd Land. Frezzotti et al (2007) show that surface slope in the prevailing wind direction (SPWD) is a key constraint in determining spatial and temporal variability of precipitation; a higher SPWD can lead to significant ablation and redeposition of snow (Frezzotti et al, 2002a(Frezzotti et al, , b, 2005(Frezzotti et al, , 2007.…”

Multi-Temporal Investigation of the Boulder Clay Glacier and Northern Foothills (Victoria Land, Antarctica) by Integrated Surveying Techniques

“…In last decades, remote sensing and geophysical investigations have been widely used, often separately, in glacier investigations allowing to achieve a large variety of information concerning the monitoring of ice front fluctuation, iceberg calving, mass balance calculation, ice flow speed, bedrock mapping and ice/bedrock interface properties [1][2][3][4][5][6][7][8].…”