http://hdl.handle.net/2122/125 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/4180 Title: Lakes and subglacial hydrological networks around Dome C, East Antarctica <br/> <br/>Authors: Rémy, F.; Laboratoire d’Etudes en Géophysique et Océanographie Spatiale, 18 avenue Edouard Belin, 31055 Toulouse Cedex, France; Testut, L.; Laboratoire d’Etudes en Géophysique et Océanographie Spatiale, 18 avenue Edouard Belin, 31055 Toulouse Cedex, France; Legrésy, B.; Laboratoire d’Etudes en Géophysique et Océanographie Spatiale, 18 avenue Edouard Belin, 31055 Toulouse Cedex, France; Forieri, A.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Cicognara 7, I-20129 Milan, Italy; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tabacco, I. E.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Cicognara 7, I-20129 Milan, Italy <br/> <br/>Abstract: Precise topography from European Remote-sensing Satellite radar altimetry and high density of airborne radio-echo sounding in the area surrounding Dome C, Antarctica, show a link between surface features and subglacial lakes. In this paper, we extend the study to fine structures by computing a curvature-based coefficient (cy) related to surface undulations. These coefficient variations reveal many surface undulations, and some elongated features of this parameter seem to link known subglacial lakes. A population of high values of this coefficient, assumed to correspond to transitions between sliding and non-sliding flow regime, strengthen the appearance of a network which would link most of the lakes in the area. The existence of such a network impacts on ice-flow dynamics and on subglacial-lake studies. http://hdl.handle.net/2122/4179 Title: Influence of geometrical boundary conditions on the estimation of rheological parameters <br/> <br/>Authors: Testut, L.; UMR5566, Groupe de Recherche de Géodésie Spatiale, CNES-CNRS, Toulouse Cedex 31055, France; Tabacco, I. E.; Dipartimento di Scienze della Terra, Università degli Studi di Milano, I-20129 Milan, Italy; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Rémy, F.; UMR5566, Groupe de Recherche de Géodésie Spatiale, CNES-CNRS, Toulouse Cedex 31055, France <br/> <br/>Abstract: Improved knowledge of geometrical boundary conditions, such as bedrock geometry and surface topography, can contribute significantly to glaciological studies including ice-sheet-flow modelling. Precise thickness and altimetric data allow an estimation of ice-flow direction, the balance velocity and the basal shear stress. These parameters are calculated along a 1160 km profile in East Antarctica using a relationship between shear stress, basal temperature, the Glen flow exponent and a parameter related to strain rate. Strong variations of the flow-law parameters and basal conditions are found to play a major role in the ice-flow pattern. Sliding, anisotropy and longitudinal stress strongly perturb the validity of the law, but their signature can be identified. http://hdl.handle.net/2122/4178 Title: Electromagnetic reflecting properties of sub-ice surfaces <br/> <br/>Authors: Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Forieri, A.; Sezione Geofisica, Università di Milano, Via Cicognara 7, I-20129 Milan, Italy; Tabacco, I. E.; Sezione Geofisica, Università di Milano, Via Cicognara 7, I-20129 Milan, Italy <br/> <br/>Abstract: The power strength of the radio-echo signal coming from reflecting sub-ice surfaces is used to determine the nature of the reflecting surface, i.e. rock, water or sea water. Electromagnetic analysis shows that the amplitude variations detected by radio-echo sounding are mainly due to the nature of the interface as well as the concave or convex shape of the reflectors. In this paper, some relevant profiles showing the power variations due to the different nature of the interface and the shape of the reflectors are presented. These results are important both for surface shape determination and for subglacial lake detection. http://hdl.handle.net/2122/4053 Title: Geophysical survey at Talos Dome, East Antarctica: the search for a new deep-drilling site <br/> <br/>Authors: Frezzotti, M.; ENEA, Centro Ricerche Casaccia, P.O. Box 2400, I-00100 Rome, Italy; Bitelli, G.; DISTART, University of Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Deponti, A.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy; Forieri, A.; Department of Earth Sciences, University of Milan, Via Cicognara 7, I-20129 Milan, Italy and Department of Earth Sciences, University of Siena, Via del Laterino 8, I-53100 Siena, Italy; Gandolfi, S.; DISTART, University of Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; Maggi, V.; Department of Environmental Sciences, University of Milano–Bicocca, Piazza della Scienza 1, I-20126 Milan, Italy; Mancini, F.; DISTART, University of Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; Remy, F.; Legos, CNRS-CNES-UPS, 18 av. Edouard Belin, 31055 Toulouse Cedex, France; Tabacco, I. E.; Department of Earth Sciences, University of Milan, Via Cicognara 7, I-20129 Milan, Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vittuari, L.; DISTART, University of Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: 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.