On the interpretation of ice-shelf flexure measurements

Tidal flexure in ice shelf grounding zones has been used extensively in the past to determine grounding line position and ice properties. Although the rheology of ice is viscoelastic at tidal loading frequencies, most modelling studies have assumed some form of linear elastic beam approximation to m...

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Bibliographic Details
Published in:Journal of glaciology 2017-10, Vol.63 (241), p.783-791
Main Authors: ROSIER, SEBASTIAN H. R., MARSH, OLIVER J., RACK, WOLFGANG, GUDMUNDSSON, G. HILMAR, WILD, CHRISTIAN T., RYAN, MICHELLE
Format: Article
Language:English
Subjects:
Approximation
Beam theory (structures)
Crevasses
Density
Elastic beams
Flexing
Ice
Ice properties
ice rheology
Ice shelves
ice-sheet modelling
ice/ocean interactions
Laboratories
Land ice
Mechanical properties
Modelling
Modulus of elasticity
Ocean loading
Profiles
Radar
Rheological properties
Rheology
Stiffness
Tidal amplitude
Viscoelasticity
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Summary:Tidal flexure in ice shelf grounding zones has been used extensively in the past to determine grounding line position and ice properties. Although the rheology of ice is viscoelastic at tidal loading frequencies, most modelling studies have assumed some form of linear elastic beam approximation to match observed flexure profiles. Here we use density, radar and DInSAR measurements in combination with full-Stokes viscoelastic modelling to investigate a range of additional controls on the flexure of the Southern McMurdo Ice Shelf. We find that inclusion of observed basal crevasses and density dependent ice stiffness can greatly alter the flexure profile and yet fitting a simple elastic beam model to that profile will still produce an excellent fit. Estimates of the effective Young's modulus derived by fitting flexure profiles are shown to vary by over 200% depending on whether these factors are included, even when the local thickness is well constrained. Conversely, estimates of the grounding line position are relatively insensitive to these considerations for the case of a steep bed slope in our study region. By fitting tidal amplitudes only, and ignoring phase information, elastic beam theory can provide a good fit to observations in a wide variety of situations. This should, however, not be taken as an indication that the underlying rheological assumptions are correct.
ISSN:0022-1430
1727-5652
DOI:10.1017/jog.2017.44