Abstract
Ice-shelf grounding zones link the Antarctic ice-sheets to the ocean. Differential interferometric synthetic aperture radar (DInSAR) is commonly used to monitor grounding-line locations, but also contains information on grounding-zone ice thickness, ice properties and tidal conditions beneath the ice shelf. Here, we combine in-situ data with numerical modelling of ice-shelf flexure to investigate 2-D controls on the tidal bending pattern on the Southern McMurdo Ice Shelf. We validate our results with 9 double-differential TerraSAR-X interferograms. It is necessary to make adjustments to the tidal forcing to directly compare observations with model output and we find that when these adjustments are small (< 1.5 cm) a viscoelastic model matches better, while an elastic model is more robust overall. Within landward embayments, where lateral stresses from surrounding protrusions damp the flexural response, a 2-D model captures behaviour that is missed in simple 1-D models. We conclude that improvements in current tide models are required to allow for the full exploitation of DInSAR in grounding-zone glaciology.
Highlights
Grounding zones form the junction between grounded ice-sheets and floating ice-shelves
The overall model performance is characterized by the standard deviation of the differences between the differential interferometric synthetic aperture radar (InSAR) (DInSAR) observations of SAR: Date, time (UTC)
We show that tidal flexure patterns in grounding zones observed using DInSAR can be reproduced within a few centimeters using finite-element modeling
Summary
Grounding zones form the junction between grounded ice-sheets and floating ice-shelves. Since Goldstein et al (1993) successfully observed glacier motion from space at the Rutford Ice Stream, Antarctica, interferometric synthetic aperture radar (InSAR) has become a widely used tool in glaciology This method determines surface displacement with centimeter accuracy and has been applied to measure temporal and spatial variations of ice-flow velocities (Mouginot et al, 2014; Minchew et al, 2017). The phase contribution of steady horizontal ice flow can be removed by differencing the 2 InSAR signals (Rignot, 1996), leaving only vertical deflection due to ocean tides These 2 InSAR pairs can be a triple or quadruple image combination of 3 or 4 coherent SAR images. This space-borne measurement is known as double-differential InSAR (DInSAR)
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