http://hdl.handle.net/2122/127 Sun, 26 May 2013 05:05:26 GMT 2013-05-26T05:05:26Z 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. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8533 2012-12-31T23:00:00Z http://hdl.handle.net/2122/7248 Title: Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year Authors: Bindschadler, R.; Code 614.0, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; Choi, H.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Wichlacz, A.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Bingham, R.; School of Geosciences, University of Aberdeen, Aberdeen, AB24 3FX, UK; Bohlander, J.; National Snow and Ice Data Center, University of Colorado, Boulder CO 80309-0449, USA; Brunt, K.; Code 614.1, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Corr, H.; British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Drews, R.; Alfred Wegener Institut for Polar and Marine Research, Postfach 12 01 61, 27515 Bremerhaven, Germany; Fricker, H.; Scripps Institute of Oceanography, University of California at San Diego, 9500 Giman Drive, La Jolla CA 92093, USA; Hall, M.; Climate Change Institute, University of Maine, Orono ME 04469, USA; Hindmarsh, R.; British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Kohler, J.; Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromso, Norway; Padman, L.; Earth and Space Research (ESR), 3350 SW Cascade Ave., Corvallis, OR 97333-1536, USA; Rack, W.; Gateway Antarctica, University of Canterbury, Private Bag, Christchurch 8140, New Zealand; Rotschky, G.; Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromso, Norway; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vornberger, P.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Young, N.; Australian Antarctic Division, University of Tasmania, Kingston, Tasmania 7050, Australia Abstract: Two ice-dynamic transitions of the Antarctic ice sheet – the boundary of grounded ice features and the freelyfloating boundary – are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74% abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea-ice covered ocean, and 7% of the boundary ice terminates on land. The freelyfloating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from ±52m for the land and open-ocean terminating segments to ±502m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of ±3.6, ±9.6, ±11.4, ±30 and ±100m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2±71.3m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center. Thu, 30 Jun 2011 22:00:00 GMT http://hdl.handle.net/2122/7248 2011-06-30T22:00:00Z http://hdl.handle.net/2122/6933 Title: Sedimentary processes on the Wilkes Land continental rise reflect changes in glacial dynamic and bottom water flow Authors: Caburlotto, A.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, OGS, Borgo grotta Gigante 42/c, 34010 Sgonico, Italy; Lucchi, R. G.; Department D’Estatrigrafia, P. i Geocie´nces Marines, Universitat de Barcelona, C/Martı´ i Franque`s, s/n, 08028 Barcelona, Spain; De Santis, L.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, OGS, Borgo grotta Gigante 42/c, 34010 Sgonico, Italy; Macrì, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tolotti, R.; Dip. Te. Ris., Universita` degli Studi di Genova, Corso Europa 26, 16132 Genoa, Italy Abstract: Four sediment cores were analysed in order to determine the sedimentary processes associated with the channel-ridge depositional system that characterise the George V Land continental margin on the Wilkes Land. The sedimentary record indicates that the WEGA channel was a dynamic turbiditic system up to M.I.S. 11. After this time, the channel became a lower-energy environment with sediments delivered to the channel through high-density bottom waters that we identify to be the high salinity shelf waters (HSSW) forming on the shelf area. The HSSW entrains the fine-grained sediments of the shelf area and deliver them to the continental rise. The biostratigraphy and facies of the sediments within the WEGA channel indicate that the HSSW down flow was active also during last glacial. The change from a turbiditic system to a lowenergy bottom current system within the WEGA channel likely reflects a different ice-flow pattern, with ice-sheet reaching the continental shelf edge only within the ice trough (ice stream). Mon, 31 May 2010 22:00:00 GMT http://hdl.handle.net/2122/6933 2010-05-31T22:00:00Z http://hdl.handle.net/2122/6205 Title: Radio echo sounding data analysis of the Shackleton Ice Shelf Authors: Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tabacco, I. E.; Università degli Studi di Milano, Dipartimento Scienze della Terra, Milano, Italy; Bottari, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Young, N.; Australian Antarctic Division, and Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Australia Abstract: 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. Wed, 31 Mar 2010 22:00:00 GMT http://hdl.handle.net/2122/6205 2010-03-31T22:00:00Z http://hdl.handle.net/2122/4251 Title: Joint Geophysical Observations of Ice Stream Dynamics Authors: Danesi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Dubbini, M.; DiMec, Università di Modena e Reggio Emilia; Morelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Vittuari, L.; DISTART, Università di Bologna; Bannister, S.; GNS Science, NZ Editors: Capra, A.; DiMec, Università di Modena e Reggio Emilia; Dietrich, R.; Technische Universitat Dresden, G Abstract: Ice streams play a major role in the ice mass balance and in the reckoning of the global sea level; they have therefore been object of wide scientific interest in the last three decades. During the 21st Italian Antarctic Expedition, in the austral summer 2005–06, we deployed a joint seismographic and geodetic network in the area of the David Glacier, Southern Victoria Land. This campaign followed a similar experiment carried out in the same area during the austral summer 2003–04 with the deployment of a seismographic network that recorded significant microseismicity beneath the David Glacier, primarily occurring as a few small clusters. In the latest 2005–06 deployment, 7 seismographic stations and 3 GPS geodetic receivers operated continuously for a period of 3 months (November 2005–early February 2006) in an area of about 100×150 km2 around the David Glacier. We have carried out several analyses using the combined data sets. These included the examination of the temporal evolution in earthquake magnitude and location and also the contemporaneous observation of both seismic activity and surface kinematics of the ice stream to possibly correlate the recorded microseismicity with the movement of the glacier, affected by the Ross Sea tides. Unfortunately, a clear correlation between the occurrence of seismic events and the movement of the glacier is not evident. Here we present some details of the two temporary networks and preliminary results and implications. Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2122/4251 2007-12-31T23:00:00Z http://hdl.handle.net/2122/4208 Title: Tidal forcing on David Glacier and Drygalski Ice Tongue Authors: Casula, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Danesi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Dubbini, M.; DIMeC, Università di Modena e Reggio Emilia; Vittuari, L.; DISTART, Università di Bologna Editors: Cooper, A.K.; Stanford University, USA; Barrett, P.; Antarctic Research Center, NZ; Stagg, H.; Geoscience Australia, AU; Storey, B.; University of Canterbury, NZ; Stump, E.; Arizona State University, USA; Wise, W.; Florida State University, USA Abstract: During the 2005-06 Austral Summer, we carried out a joint observational campaign in the area of the David Glacier, South Victoria Land, with the aim of collecting simultaneous time series of geodetic and seismological data. We installed 7 temporary seismographic stations on rock outcrops surrounding the glacier and 3 temporary geodetic stations both on flowing ice and on rock. The seismic network registered a significant low-energy seismic activity, principally originated by ice creeping and basal stress at the interface between the ice and the bedrock. The geodetic stations allowed us to survey the glacier kinematics forced by the Ross Sea tides, and to infer the grounding line location. Here we show some details about data analysis and preliminary results. Sat, 25 Aug 2007 22:00:00 GMT http://hdl.handle.net/2122/4208 2007-08-25T22:00:00Z 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. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2122/4180 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. Fri, 31 Dec 1999 23:00:00 GMT http://hdl.handle.net/2122/4179 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. Wed, 31 Dec 2003 23:00:00 GMT http://hdl.handle.net/2122/4178 2003-12-31T23:00:00Z http://hdl.handle.net/2122/4066 Title: Snow dunes and glazed surfaces in Antarctica: new field and remote-sensing data Authors: Frezzotti, M.; ENEA, Centro Ricerche Casaccia, P.O. Box 2400, I-00100 Rome, Italy; Gandolfi, S.; DISTART, Università di Bologna, Viale Risorgimento 2, I-40136 Bologna, Italy; La Marca, F.; Dipartimento di ICMMPM, Università di Roma "La Sapienza", Via Eudossiana 18, I-00184 Rome, Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic Programme undertook two traverses from the Terra Nova station to Talos Dome and to Dome C. Along the traverses, the party carried out several tasks (drilling, glaciological and geophysical exploration). The difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible/near-infrared satellite images. Integration of field observation and remotely sensed data allows the description of different mega-morphologic features: wide glazed surfaces, sastrugy glazed surface fields, transverse dunes and megadunes. Topography global positioning system, ground penetrating radar and detailed snow-surface surveys have been carried out, providing new information about the formation and evolution of mega-morphologic features. The extensive presence, (up to 30%) of glazed surface caused by a long hiatus in accumulation, with an accumulation rate of nil or slightly negative, has a significant impact on the surface mass balance of a wide area of the interior part of East Antarctica. The aeolian processes creating these features have important implications for the selection of optimum sites for ice coring, because orographic variations of even a few metres per kilometre have a significant impact on the snow-accumulation process. Remote-sensing surveys of aeolian macro-morphology provide a proven, high-quality method for detailed mapping of the interior of the ice sheet's prevalent wind direction and could provide a relative indication of wind intensity. Mon, 31 Dec 2001 23:00:00 GMT http://hdl.handle.net/2122/4066 2001-12-31T23:00:00Z