Tidally induced velocity variations of the beardmore glacier

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TitleTidally induced velocity variations of the beardmore glacier, Antarctica, and their representation in satellite measurements of ice velocityAbstractOcean tides close to the grounding line of outlet glaciers around Antarctica have been shown to directly influence ice velocity, both linearly and non-linearly. These fluctuations can be significant and have the potential to affect satellite measurements of ice discharge, which assume displacement between satellite passes to be consistent and representative of annual means. Satellite observations of horizontal velocity variation in the grounding zone are also contaminated by vertical tidal effects, the importance of which is highlighted here in speckle tracking measurements. Eight TerraSAR-X scenes from the grounding zone of the Beardmore Glacier are analysed in conjunction with GPS measurements to determine short-term and decadal trends in ice velocity. Diurnal tides produce horizontal velocity fluctuations of >50% on the ice shelf, recorded in the GPS data 4 km downstream of the grounding line. This variability decreases rapidly to <5% only 15 km upstream of the grounding line. Daily fluctuations are smoothed to <1% in the 11-day repeat pass TerraSAR-X imagery, but fortnightly variations over this period are still visible and show that satellite-velocity measurements can be affected by tides over longer periods. The measured tidal displacement observed in radar look direction over floating ice also allows the grounding line to be identified, using differential speckle tracking where phase information cannot be easily unwrapped. © Author(s) 2013.AcknowledgementsTerraSAR-X data were provided by DLR from science proposal HYD1421. ASTER data were provided through the GLIMS project. Fieldwork on the Beardmore Glacier was supported by the US Antarctic Program, Antarctica New Zealand Event K001BI and with assistance from Dean Arthur. Weather station data were provided by the UW-Madison AWS Program. This research was funded, in part, by the Ministry of Business, Innovation and Employment through research contract CO5X1001 to GNS Science. Comments by two anonymous reviewers led to revisions and improvement of the paper.

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1st AuthorMarsh, O.AuthorMarsh, O.Rack, W.Floricioiu, D.Golledge, N.Lawson, W.Year2013JournalCryosphereVolume7Number5Pages1375-1384DOI10.5194/tc-7-1375-2013URLhttps://www.scopus.com/inward/recor.....b685658003c81012a306f912eKeywordsglacial environmentGPSidentification methodmeasurement methodnonlinearitysatellite datasatellite imageryTerraSAR-Xtidal cyclevelocity, Antarctica, rank5

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TypeArticleCitationMarsh, O., Rack, W., Floricioiu, D., Golledge, N. and Lawson, W. (2013). Tidally induced velocity variations of the beardmore glacier, Antarctica, and their representation in satellite measurements of ice velocity. Cryosphere, 7(5): 1375-1384 doi:10.5194/tc-7-1375-2013 IdentifierMarsh2013Relevancerank5