Getting around Antarctica: New high-resolution mappings of t

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TitleGetting around Antarctica: New high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar YearAbstractTwo ice-dynamic transitions of the Antarctic ice sheet-the boundary of grounded ice features and the freely-floating 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 freely-floating 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 Â±52 m for the land and open-ocean terminating segments to Â±502 m 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 ±100 m 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 &pm; 71.3 m 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. Copyright 2011 Author(s).AcknowledgementsA project of this magnitude and complexity could not have been accomplished without extensive contributions from many people, some of whom do not appear as authors on this paper. Funding support for the central work was provided through NASA grant 509496.02.08.01.81. Other domestic and international participants have been supported by other funding and we thank the British Antarctic Survey for adding flights specifically for ASAID to an already packed field schedule. Michiel van den Broeke was extremely gracious for providing his work on firn correction values. Two anonymous reviewers contributed persuasive criticisms of an earlier draft that led to the extensive use of BEDMAP-compiled data and greatly improved the quantitative assessment of the ASAID products Ìaccuracies.

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1st AuthorBindschadler, R.AuthorBindschadler, 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.Year2011JournalCryosphereVolume5Number3Pages569-588DOI10.5194/tc-5-569-2011URLhttps://www.scopus.com/inward/recor.....4f437a1011005c38ccbd2f2b3Keywordsaccuracy assessmentamplitudecomparative studydata setdigital elevation modelglacierhydrostaticsice sheetice thicknessLandsatmagnitudemapping methodoscillationquantitative analysisresolutionsea icesoftware, Antarctica, rank3

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TypeArticleCitationBindschadler, 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. and Young, N. (2011). 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. Cryosphere, 5(3): 569-588 IdentifierBindschadler2011Relevancerank3