Evidence that seismic anisotropy captures upstream palaeo ice fabric: Implications on present day deformation at Whillans Ice Stream, Antarctica

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.31223/X54961. This is version 2 of this Preprint.

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Authors

Justin Leung, Thomas Samuel Hudson , John-Michael Kendall, Grace Barcheck

Abstract

Understanding deformation and slip at ice streams, which are responsible for 90% of Antarctic ice loss, is vital for accurately modelling large-scale ice flow. Ice preferred crystal orientation fabric (COF) has a first-order effect on ice stream deformation. For the first time, we use shear-wave splitting (SWS) measurements of basal icequakes at Whillans Ice Stream (WIS), Antarctica, to determine a shear-wave anisotropy with an average delay time of 7 ms and fast S-wave polarisation (φ) of 29.3º. The polarisation is expected to align perpendicular to ice flow, whereas our observation is oblique to the current ice flow direction (~280º). Our results suggest that ice at WIS preserves upstream fabric caused by palaeo-deformation developed over at least the past 450 years, implying that changes in the shape of WIS occurs on timescales shorter than COF re-equilibration. The “palaeo-fabric” can somewhat control present-day ice flow, which we suggest may somewhat counteract the long-term slowdown at WIS. Our findings suggest that seismic anisotropy can provide information on past ice sheet dynamics, and how past ice dynamics can play a role in controlling current deformation.

DOI

https://doi.org/10.31223/X54961

Subjects

Earth Sciences, Geophysics and Seismology, Glaciology, Physical Sciences and Mathematics

Keywords

Icequakes, ice streams, Seismology, Anisotropic Ice

Dates

Published: 2023-11-16 07:25

Last Updated: 2024-02-12 17:10

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License

CC BY Attribution 4.0 International