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Young, N. W.
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- PublicationOpen AccessRadio echo sounding data analysis of the Shackleton Ice Shelf(2010-04)
; ; ; ; ; ; ; ;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; ; ; ; ; ; 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.14928 287 - PublicationOpen AccessGravimetric Constraints on the Hydrothermal System of the Campi Flegrei CalderaThe Campi Flegrei caldera (Italy) has been undergoing unrest over the past five decades including episodes of rapid ground deformation, seismicity, and variations in gas emissions. Hydrothermal fluids and gases are released most vigorously in the central sector of the caldera at the fumarolic fields of Solfatara volcano and Pisciarelli. We conducted a high‐precision gravity survey coupledwith inverse modeling to image the shallow (<2‐km depth) structure of the hydrothermal feeder system. Results indicate the presence of three low density bodies beneath Pozzuoli, Astroni volcano and the Solfatara/Pisciarelli fumarolic fields. The first two are inferred to be sealed hydrothermal systems trapped beneath impermeable cap rock, while the latter depicts a plume‐like geothermal feeder system reaching the surface via a combination of Solfatara's maar‐diatreme structure and the intersection of NW‐SE and NE‐SW trending regional faults. The density contrasts of the reservoirs from background values are best explained by a multiphase mixture of caldera fill containing a secondary and interconnected void volume fraction of between 0.2 and 0.3 that hosts a vapor volume fraction ψv of between 0.38 and 1 and a liquid volume fraction ψl fraction of between 0 and 0.62. This work highlights the control of volcano‐tectonic structures on fluid movement in the shallow crust of hydrothermally active volcanic systems undergoing sustained or periodic unrest.
59 16 - PublicationOpen AccessGetting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year(2011-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;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; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; 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.738 387 - PublicationOpen AccessRefined broad-scale sub-glacial morphology of Aurora Subglacial Basin, East Antarctica derived by an ice-dynamics-based interpolation scheme(2011-07-13)
; ; ; ; ; ; ; ; ; ; ; ; ; ;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; ; ; ; ; ; ; ; ; ; ; ; 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.705 170