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TitleInterferometric swath processing of Cryosat data for glacial ice topography
AuthorGray, L; Burgess, D; Copland, L; Cullen, R; Galin, N; Hawley, R; Helm, V
SourceThe Cryosphere vol. 7, 2013 p. 1857-1867,
Alt SeriesEarth Sciences Sector, Contribution Series 20130133
Mediapaper; on-line; digital
File formatpdf
Subjectsgeophysics; surficial geology/geomorphology; ice; glacial deposits; topography; terrain types
Illustrationsplots; histograms; images
ProgramProgram Coordination - Climate Change Science, Climate Change Geoscience
AbstractWe have derived digital elevation models (DEMs) over the western part of the Devon Ice Cap in Nunavut, Canada, using "swath processing" of interferometric data collected by Cryosat between February 2011 and January 2012. With the standard ESA (European Space Agency) SARIn (synthetic aperture radar interferometry) level 2 (L2) data product, the interferometric mode is used to map the cross-track position and elevation of the "point-of-closestapproach" (POCA) in sloping glacial terrain. However, in this work we explore the extent to which the phase of the returns in the intermediate L1b product can also be used to map the heights of time-delayed footprints beyond the POCA. We show that there is a range of average cross-track slopes ( 0.5 to 2 ) for which the returns will be dominated by those beneath the satellite in the main beam of the antenna so that the resulting interferometric phase allows mapping of heights in the delayed range window beyond the POCA. In this way a swath of elevation data is mapped, allowing the creation of DEMs from a sequence of L1b SARIn Cryosat data takes. Comparison of the Devon results with airborne scanning laser data showed a mean difference of order 1m with a standard deviation of about 1 m. The limitations of swath processing, which generates almost 2 orders of magnitude more data than traditional radar altimetry, are explored through simulation, and the strengths and weaknesses of the technique are discussed.
Summary(Plain Language Summary, not published)
The CryoSat-2 radar altimeter is a European Space Agency initiative that will play an integral role in Canada's scaled glacier-climate observing approach, contributing to Climate Change Geoscience Program objectives through provision of data on glacier mass change as it concerns freshwater flux to oceans. Preliminary results of the L1b SARin processed data from the Devon ice cap, Nunavut reveal strong potential for Cryosat-2 to provide high spatial and temporal elevation data over small polar ice caps characteristic of those in Canada's high Arctic. Current processing and validation reveal spatially varying biases on the order of 1 meter, and additional biases between ascending and descending mode data. Work towards further reducing these errors is underway.