Measurements and modelling of tidal ice-shelf flexure in Antarctic grounding zones

• Main Author: Wild, Christian T.
• Format: Other/Unknown Material
• Language: English
• Published: University of Canterbury 2018
• Subjects: Antarctic; The Antarctic; Antarc*; Antarctica; Ice Shelf
• Online Access: http://hdl.handle.net/10092/17521; https://doi.org/10.26021/8203

As regions of Antarctica undergo rapid melting, the inflow of freshwater leads to global sea level rise, but what exactly is Antarctica’s contribution? Current satellites cannot measure ice discharge directly, but they can be used to observe processes on the surface, including, how the ice bends up and down with the tides as it flows from the continent into the ocean. Measuring this surface bending along the Antarctic coastline can then indirectly determine the ice flow underneath, but this connection requires knowledge of the physical properties of ice as well as accurate prediction of the tidal oscillation in coastal areas. However, the behaviour of ice when subjected to a tidal forcing is uncertain, and complicated even further by inherently inaccurate predictions of tide models around Antarctica. Laboratory measurements of glacial ice properties deviate largely from field observations both in space and time, and modern tide models are still most inaccurate in coastal areas. These limitations currently constrain our knowledge about ice-ocean interaction from a regional to a continental scale and directly affect the reliability of predictions of future sea-level rise. The present thesis targets these issues by combining a range of satellite remote-sensing techniques with state-of-the-art finite-element modelling and traditional field measurements in Antarctica. This synergistic approach allows to uncover the physical properties of ice when responding to a tidal forcing. Previously reported, unphysical, temporal changes of the Young’s modulus for Antarctic ice can be explained with a systematical artefact of the representation of viscous damping in an elastic model for tidal flexure. Further numerical simulations reveal that a viscoelastic model fits tiltmeter measurements closely using a constant Young’s modulus of 1.6 GPa and an ice viscosity of ͌ 50.1 TPa s. With this level of insight in ice rheology, other factors influencing tidal ice-shelf flexure can be explored to further investigate ...