The Frontier Mountain meteorite gap (Antarctica)

The Frontier Mountain blue ice field is an important Antarctic meteorite trap which has yielded 472 meteorite specimens since its discovery in 1984. Remote sensing analyses and field campaigns from 1993 to 1999 have furnished new glaciological data on ice flow, ice thickness, bedrock topography, ice ablation and surface mass transport by wind, along with detailed descriptions of the field situation at the trap. This solid set of data combined with an updated meteorite distribution map and terrestrial ages available from literature allows us to better describe the nature of the concentration mechanism. In particular, we observe that the meteorite trap forms in a blue ice field i) located upstream of an absolute and a shallow subice barriers; ii) characterized by compressive ice flow with horizontal velocities decreasing from 100 to <10 cm a-1 on approaching the obstacle; iii) undergoing mean ablation rates of 6.5 cm a-1; iv) nourished by a limited snow accumulation zone extending ~20 km upstream of the blue ice area. We also draw the following conclusions: i) the origin of the meteorite trap can be explained according to the present-day glaciological situation; ii) the meteorite concentration develops according to the general principles of the “ice flow model”; iii) the accumulation model can be described as “stagnant ice or slow-moving ice against an absolute and submerged barriers”, according to the descriptive schemes present in literature; iv) the Frontier Mountain ice field is an effective trap for meteorites weighing more than ~200 g; for smaller masses, the combination of wind and glacial drift may remove meteorites in less than a few tens of ka; v) although the activation age of the FM trap is not yet constrained, we infer that one of the most important findsite may be as old as 50 ka, i.e. older than the Last Glacial Maximum

Evidence for Possible New Subglacial Lakes along a Radar Transect Crossing the Belgica Highlands and the Concordia Trench

Subglacial lakes are of great interest to the scientific community, and about 190 lakes have been identified in Antarctica and catalogued (Siegert et al., 2005; Cafarella et al., 2006; Popov & Masolov, 2007). We report on the possible existence of 5 new subglacial lakes in the area between the Belgica HighLands and the Concordia Trench. Analysis of radar data collected during the 2003 Antarctic field survey reveals particularly strong radar echoes coming from the subglacial interface. As radar surveys are only one of the methods used to identify subglacial lakes, the presence of these 5 new lakes must be discussed and confirmed through other geophysical investigations

Italian RES Investigation in Antarctica: The New Radar System

A Radio Echo Sounding (RES) system is an active remote-sensing instrument that uses electromagnetic wave penetration into the ice to obtain information on the depth of the bedrock and on the ice thickness and its inhomogeneities, i.e. internal layering of glaciers and subglacial lake exploration. In 1995 the INGV developed its own airborne radio echo sounding system, which is continuously being upgraded. During the 1995, 1997, 1999, 2001 and 2003 Italian Antarctic Expeditions, the RES system was used to investigate different Antarctic regions. During 2007-2008 campaign, new RES systems will be used. In the following the main characteristics of the systems will be briefly described

Radio Echo Sounding (RES) investigations at Talos Dome (East Antarctica): bedrock topography and ice thickness

Radio echo sounding measurements were collected during two Antarctic expeditions to determine the ice thickness and the sub-glacial morphology of Talos Dome in the region around 72°48'S; 159°06'E (about 6400 km2) on the edge of the East Antarctic plateau adjacent to Victoria Land in the western Ross Sea sector. The increasing interest in this region is due to the fact that in this area the ice accumulation is higher than in other sites in East Antarctica. Because of this, Talos Dome could be a new site for a project of a deep ice core drilling to obtain information on climate changes near the coast of Antarctica. In this frame, the knowledge of the bedrock topography is of great importance to choose the best location for the drilling site. In this paper, airborne radio echo sounding results from two Antarctic expeditions (1997 and 1999) are presented. Bedrock topography in bi- and three-dimensions for the Talos Dome region are discussed

Radio echo sounding data analysis of the Shackleton Ice Shelf

In this study, our initial results are presented for the interpretation of the radio echo sounding data collected over the Shackleton Ice Shelf and adjacent ice sheet (East Antarctica) during the 2003/2004 Australian- Italian expedition. The Shackleton Ice Shelf is one of the larger ice shelves of the East Antarctic Ice Sheet. The radar survey provided data relating to ice thickness and bed morphology of the outlet glaciers, and thickness of their floating portions. The glacier grounding lines were determined by assessment of the basal echo characters. The information derived is compared with data from the BEDMAP database and from other sources

RES Investigation of the Aurora Basin Area (East Antarctica)

We analyse radio echo sounding (RES) data on the region between Lake Vostok and the Belgica Subglacial Highlands (East Antarctica) collected during four Italian expeditions (1995, 1999, 2001 and 2003). The survey aimed to define the morphological characteristics of the Aurora Trench and to aid the exploration of subglacial lakes

Geophysical survey at Talos Dome, East Antarctica: the search for a new deep-drilling site

Talos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is higher here than in other domes of East Antarctica, the ice preserves a good geochemical and palaeoclimatic record. A new map of the Talos Dome area locates the dome summit using the global positioning system (GPS) (72˚47’ 14’’S, 159˚04’ 2’’E; 2318.5m elevation (WGS84)). A surface strain network of nine stakes was measured using GPS. Data indicate that the stake closest to the summit moves south-southeast at a few cma–1. The other stakes, located 8 km away, move up to 0.33ma–1. Airborne radar measurements indicate that the bedrock at the Talos Dome summit is about 400m in elevation, and that it is covered by about 1900m of ice. Snow radar and GPS surveys show that internal layering is continuous and horizontal in the summit area (15 km radius). The depth distribution analysis of snow radar layers reveals that accumulation decreases downwind of the dome (north-northeast) and increases upwind (south-southwest). The palaeomorphology of the dome has changed during the past 500 years, probably due to variation in spatial distribution of snow accumulation, driven by wind sublimation. In order to calculate a preliminary age vs depth profile for Talos Dome, a simple one-dimensional steady-state model was formulated. This model predicts that the ice 100m above the bedrock may cover one glacial–interglacial period.Published423-4323.8. Geofisica per l'ambienteJCR Journalreserve

Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme

Ice thickness data over much of East Antarctica are sparse and irregularly distributed. This poses difficulties for reconstructing the homogeneous coverage needed to properly assess underlying sub-glacial morphology and fundamental geometric constraints on sea level rise. Here we introduce a new physically-based ice thickness interpolation scheme and apply this to existing ice thickness data in the Aurora Subglacial Basin region. The skill and robustness of the new reconstruction is demonstrated by comparison with new data from the ICECAP project. The interpolated morphology shows an extensive marine-based ice sheet, with considerably more area below sea-level than shown by prior studies. It also shows deep features connecting the coastal grounding zone with the deepest regions in the interior. This has implications for ice sheet response to a warming ocean and underscores the importance of obtaining additional high resolution data in these marginal zones for modelling ice sheet evolution

Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme

Ice thickness data over much of East Antarctica are sparse and irregularly distributed. This poses difficulties for reconstructing the homogeneous coverage needed to properly assess underlying sub-glacial morphology and fundamental geometric constraints on sea level rise. Here we introduce a new physically-based ice thickness interpolation scheme and apply this to existing ice thickness data in the Aurora Subglacial Basin region. The skill and robustness of the new reconstruction is demonstrated by comparison with new data from the ICECAP project. The interpolated morphology shows an extensive marine-based ice sheet, with considerably more area below sea-level than shown by prior studies. It also shows deep features connecting the coastal grounding zone with the deepest regions in the interior. This has implications for ice sheet response to a warming ocean and underscores the importance of obtaining additional high resolution data in these marginal zones for modelling ice sheet evolution