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
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus GmbH 2011
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Ice Shelves; International Polar Year; Sea ice
• Online Access: https://doi.org/10.5194/tc-5-569-2011; http://ecite.utas.edu.au/77999

Two ice-dynamic transitions of the Antarctic icesheet the boundary of grounded ice features and the freelyfloatingboundary are mapped at 15-m resolution by participantsof the International Polar Year project ASAID usingcustomized software combining Landsat-7 imagery andICESat/GLAS laser altimetry. The grounded ice boundary is53 610 km long; 74% abuts to floating ice shelves or outletglaciers, 19% is adjacent to open or sea-ice covered ocean,and 7% of the boundary ice terminates on land. The freelyfloatingboundary, called here the hydrostatic line, is the mostlandward position on ice shelves that expresses the full amplitudeof oscillating ocean tides. It extends 27 521 km andis discontinuous. Positional (one-sigma) accuracies of thegrounded ice boundary vary an order of magnitude rangingfrom 52m for the land and open-ocean terminating segmentsto 502m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevationsalong each line are selected from 6 candidate digitalelevation models based on their agreement with ICESat elevationvalues and surface shape inferred from the Landsatimagery. Elevations along the hydrostatic line are convertedto ice thicknesses by applying a firn-correction factor and aflotation criterion. BEDMAP-compiled data and other airbornedata are compared to the ASAID elevations and icethicknesses to arrive at quantitative (one-sigma) uncertaintiesof surface elevations of 3.6, 9.6, 11.4, 30 and100m for five ASAID-assigned confidence levels. Overone-half of the surface elevations along the grounded iceboundary and over one-third of the hydrostatic line elevationsare ranked in the highest two confidence categories.A comparison between ASAID-calculated ice shelf thicknessesand BEDMAP-compiled data indicate a thin-ice biasof 41.271.3m for the ASAID ice thicknesses. The relationshipbetween the seaward offset of the hydrostatic linefrom the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped productsalong with the customized software to generate them and avariety of intermediate products are available from the NationalSnow and Ice Data Center.