Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2017-13
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
23 Feb 2017
Review status
This discussion paper is under review for the journal The Cryosphere (TC).
Analysis of ice shelf flexure and its InSAR representation in the grounding zone of the Southern McMurdo Ice Shelf
Wolfgang Rack1, Matt A. King2, Oliver J. Marsh1, Christian T. Wild1, and Dana Floricioiu3 1Gateway Antarctica, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
2School of Land and Food, University of Tasmania, Private Bag 76, Hobart 7001, Australia
3Earth Observation Center, German Aerospace Centre (DLR) Oberpfaffenhofen, 82234 Wessling, Germany
Abstract. We examine tidal flexure in the grounding zone of the McMurdo Ice Shelf, Antarctica, using a combination of a TerraSAR-X repeat-pass radar interferometry, a precise digital elevation model, and GPS ground validation data. Satellite and field data were acquired in tandem between October and December 2014. Our GPS data show a horizontal modulation of up to 60 % of the vertical amplitude at tidal periods within a few km of the grounding line. We ascribe this to bending stresses and account for it using a simple elastic beam model. The horizontal surface strain is removed from nine differential interferograms to obtain precise vertical bending curves. This processing step allows us to identify a fixed (as opposed to tidally migrating) grounding line position and eliminates the possibility of significant upstream bending at this location. The change in apparent vertical motion due to horizontal strain can lead to a systematic mis-location of the interferometric grounding line by the order of up to one ice thickness, or several hundred metres. While our field site was selected in consideration of the simple boundary conditions and low background velocity the findings are relevant to other satellite-based grounding zone studies, particularly those looking at tidally-induced velocity changes or interpreting satellite-based flexure profiles.

Citation: Rack, W., King, M. A., Marsh, O. J., Wild, C. T., and Floricioiu, D.: Analysis of ice shelf flexure and its InSAR representation in the grounding zone of the Southern McMurdo Ice Shelf, The Cryosphere Discuss., doi:10.5194/tc-2017-13, in review, 2017.
Wolfgang Rack et al.
Wolfgang Rack et al.
Wolfgang Rack et al.

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Short summary
Predicting changes of the Antarctic ice sheet involves fully understanding ice dynamics at the transition between grounded and floating ice. We map tidal bending of ice by satellite using InSAR and we use precise GPS measurements with assumptions of tidal elastic bending to better interpret the satellite signal. It allows us to better define the grounding line position and to refine the shape of tidal flexure profiles.
Predicting changes of the Antarctic ice sheet involves fully understanding ice dynamics at the...
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