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

• Published in: The Cryosphere
• Main Authors: Bindschadler, R., Choi, H., Wichlacz, A., Bingham, R., Bohlander, J., Brunt, K., Corr, H., Drews, R., Fricker, H., Hall, M., Hindmarsh, R., Kohler, J., Padman, L., Rack, W., Rotschky, G., Urbini, S., Vornberger, P., Young, N.
• Other 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, Code 614.0, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA, SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3FX, UK, National Snow and Ice Data Center, University of Colorado, Boulder CO 80309-0449, USA, Code 614.1, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA, British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK, Alfred Wegener Institut for Polar and Marine Research, Postfach 12 01 61, 27515 Bremerhaven, Germany, Scripps Institute of Oceanography, University of California at San Diego, 9500 Giman Drive, La Jolla CA 92093, USA, Climate Change Institute, University of Maine, Orono ME 04469, USA, Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromso, Norway, Earth and Space Research (ESR), 3350 SW Cascade Ave., Corvallis, OR 97333-1536, USA, Gateway Antarctica, University of Canterbury, Private Bag, Christchurch 8140, New Zealand, Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Australian Antarctic Division, University of Tasmania, Kingston, Tasmania 7050, Australia
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Pubblications 2011
• Subjects: Antarctica; ice sheet; photoclinometry; freely-floating boundaries; 02. Cryosphere::02.02. Glaciers::02.02.05. Ice dynamics; 02. Cryosphere::02.02. Glaciers::02.02.06. Mass balance; 02. Cryosphere::02.02. Glaciers::02.02.07. Ocean/ice interaction; Antarctic; The Antarctic; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves; International Polar Year; Polar geoscience; Sea ice; The Cryosphere
• Online Access: http://hdl.handle.net/2122/7248; https://doi.org/10.5194/tc-5-569-2011

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 ...