On the interpretation of ice-shelf flexure measurements

Type of content
Journal Article
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Publisher
Journal Title
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Language
Date
2017
Authors
Rosier, Sebastian H R
Marsh, Oliver J
Rack, Wolfgang
Gundmundsson, G Hilmar
Wild, Christian T
Ryan, Michelle
Abstract

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.

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Citation
ROSIER SEBASTIAN H R, MARSH OLIVER J, RACK WOLFGANG, GUDMUNDSSON G HILMAR, WILD CHRISTIAN T, RYAN MICHELLE On the interpretation of ice-shelf flexure measurements. Journal of Glaciology. 1-9.
Keywords
ice/ocean interactions, ice shelves, ice rheology, ice-sheet modelling
Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
Fields of Research::37 - Earth sciences::3709 - Physical geography and environmental geoscience::370902 - Glaciology
Rights
© The Author(s) 2017. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.