http://hdl.handle.net/2122/126 2013-05-21T07:34:59Z http://hdl.handle.net/2122/8533 Title: Bedmap2: improved ice bed, surface and thickness datasets for Antarctica Authors: Fretwell, P.; British Antarctic Survey, Cambridge, UK; Pritchard, H. D.; British Antarctic Survey, Cambridge, UK; Vaughan, D. G.; British Antarctic Survey, Cambridge, UK; Bamber, J. L.; School of Geographical Sciences, University of Bristol, UK; Barrand, N. E.; British Antarctic Survey, Cambridge, UK; Bell, R.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, USA; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bingham, R. G.; School of Geosciences, University of Aberdeen, UK; Blankenship, D. D.; Institute for Geophysics, University of Texas at Austin, USA; Casassa, G.; Centro de Estudios Cientificos, Santiago, Chile; Catania, G.; Institute for Geophysics, University of Texas at Austin, USA; Callens, D.; Laboratoire de Glaciologie, Universit´e Libre de Bruxelles, Brussels, Belgium; Conway, H.; Earth and Space Sciences, University of Washington, Seattle, USA; Cook, A. J.; Department of Geography, Swansea University, Swansea, UK; Corr, H. F. J.; British Antarctic Survey, Cambridge, UK; Damaske, D.; Federal Institute for Geosciences and Natural Resources, Hannover, Germany; Damm, V.; Federal Institute for Geosciences and Natural Resources, Hannover, Germany; Ferraccioli, F.; British Antarctic Survey, Cambridge, UK; Forsberg, R.; National Space Institute, Technical University of Denmark, Denmark; Fujita, S.; National Institute of Polar Research, Tokyo, Japan; Gim, Y.; Jet Propulsion Laboratory. California Institute of Technology, Pasadena, USA; Gogineni, P.; Electrical Engineering & Computer Science, University of Kansas, Lawrence, USA; Griggs, J. A.; School of Geographical Sciences, University of Bristol, UK; Hindmarsh, R. C. A.; British Antarctic Survey, Cambridge, UK; Holmlund, P.; Stockholm University, Stockholm, Sweden; Holt, J. W.; Institute for Geophysics, University of Texas at Austin, USA; Jacobel, R. W.; St. Olaf College, Northfield, MN 55057, USA; Jenkins, A.; British Antarctic Survey, Cambridge, UK; Jokat, W.; Alfred Wegener Institute, Bremerhaven, Germany; Jordan, T.; British Antarctic Survey, Cambridge, UK; King, E. C.; British Antarctic Survey, Cambridge, UK; Kohler, J.; Norwegian Polar Institute, Fram Centre, Tromsø, Norway; Krabill, W.; NASA Wallops Flight Facility, Virginia, USA; Riger-Kusk, M.; College of Science, University of Canterbury, Christchurch, New Zealand; Langley, K. A.; Department of Geosciences, University of Oslo, Norway; Leitchenkov, G.; Institute for Geology and Mineral Resources of the World Ocean, St.-Petersburg, Russia; Leuschen, C.; Electrical Engineering & Computer Science, University of Kansas, Lawrence, USA; Luyendyk, B. P.; Earth Research Institute, University of California in Santa Barbara, USA; Matsuoka, K.; Norwegian Polar Institute, Tromso, Norway; Mouginot, J.; Department of Earth System Science, University of California, Irvine, USA; Nitsche, F. O.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, USA; Nogi, Y.; National Institute of Polar Research, Tokyo, Japan; Nost, O. A.; Norwegian Polar Institute, Tromso, Norway; Popov, S. V.; Polar Marine Geosurvey Expedition, St.-Petersburg, Russia; Rignot, E.; School of Physical Sciences, University of California, Irvine, USA; Rippin, D. M.; Environment Department, University of York, Heslington, York, YO10 5DD, UK; Rivera, A.; Centro de Estudios Cientificos, Santiago, Chile; Roberts, J.; Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia; Ross, N.; School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK; Siegert, M. J.; School of Geographical Sciences, University of Bristol, UK; Smith, A. M.; British Antarctic Survey, Cambridge, UK; Steinhage, D.; Alfred Wegener Institute, Bremerhaven, Germany; Studinger, M.; NASA Goddard Space Flight Center, Greenbelt, USA; Sun, B.; Polar Research Institute of China, Shanghai, China; Tinto, B. K.; Lamont-Doherty Earth Observatory of Columbia University, Palisades, USA; Welch, B. C.; Alfred Wegener Institute, Bremerhaven, Germany; Wilson, D.; Institute for Crustal Studies, University of California in Santa Barbara, USA; Young, D. A.; Institute for Geophysics, University of Texas at Austin, USA; Xiangbin, C.; Polar Research Institute of China, Shanghai, China; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved datacoverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km3) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72m lower and the area of ice sheet grounded on bed below sea level is increased by 10 %. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets. 2012-12-31T23:00:00Z http://hdl.handle.net/2122/7732 Title: Refined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme Authors: Roberts, J. L.; Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia and Antarctic Climate and Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania 7001, Australia; Warner, R. C.; Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia and Antarctic Climate and Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania 7001, Australia; Young, D.; Institute of Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA; Wright, A.; School of GeoSciences, University of Edinburgh Edinburgh, Scotland, UK; van Ommen, T. D.; Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia and Antarctic Climate and Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania 7001, Australia; Blankenship, D. D.; Institute of Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas, USA; Siegert, M.; School of GeoSciences, University of Edinburgh Edinburgh, Scotland, UK; Young, N. W.; Department of Sustainability, Environment, Water, Population and Communities, Australian Antarctic Division, Hobart, Tasmania, Australia and Antarctic Climate and Ecosystems Cooperative Research Centre, Private Bag 80, Hobart, Tasmania 7001, Australia; Tabacco, I. E.; Geofisica, Universita di Milano, Milan, Italy; Forieri, A.; Geofisica, Universita di Milano, Milan, Italy; Passerini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Frezzotti, M.; Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile, Rome, Italy Abstract: 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. 2011-07-12T22:00:00Z http://hdl.handle.net/2122/4180 Title: Lakes and subglacial hydrological networks around Dome C, East Antarctica 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 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. 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4179 Title: Influence of geometrical boundary conditions on the estimation of rheological parameters 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 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. 1999-12-31T23:00:00Z http://hdl.handle.net/2122/4178 Title: Electromagnetic reflecting properties of sub-ice surfaces 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 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. 2003-12-31T23:00:00Z http://hdl.handle.net/2122/4053 Title: Geophysical survey at Talos Dome, East Antarctica: the search for a new deep-drilling site 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 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. 2003-12-31T23:00:00Z http://hdl.handle.net/2122/3573 Title: On the shape of reflecting surfaces investigated by a 60 MHz radar Authors: Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tabacco, I. E.; Universita` di Milano — Sezione Geofisica, Milan, Italy; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Radio echo sounding (RES) systems for ice thickness measurements are practically the only suitable equipment for large-scale radar flight surveys in polar regions. The length of the radio wave carrier does not allow the employment of sophisticated antennas, so folded dipoles are used, arranged beneath the wings. As a consequence, the transmitted radio wave beam illuminates a relatively large area, making the power of the echo signal related in a significant way to the shape of the reflecting surfaces. An electromagnetic analysis shows that the amplitude variations detected by the system, under certain conditions, are mainly due to focusing or defocusing effects determined by the shape of the reflectors. 2002-12-31T23:00:00Z