EGU21-2107
https://doi.org/10.5194/egusphere-egu21-2107
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Polarimetric radar-sounding to infer and quantify shear margin ice fabric anisotropy

Tun Jan Young1, Thomas M Jordan2, Carlos Martín3, Dustin M Schroeder4, Poul Christoffersen1, Slawek M Tulaczyk5, Riley Culberg4, and Nicole L Bienert4
Tun Jan Young et al.
  • 1University of Cambridge, Scott Polar Research Institute, Cambridge, United Kingdom
  • 2Plymouth Marine Laboratory, Plymouth, United Kingdom
  • 3British Antarctic Survey, Cambridge, United Kingdom
  • 4Stanford University, Stanford CA, USA
  • 5University of California, Santa Cruz, Santa Cruz CA, USA

Glaciers and ice streams channel the majority of ice mass discharge into the ocean, and are modulated by basal slip at the ice-bed interface, deformation within the ice interior, and lateral shear at the margins separating fast- and slow-moving ice. The anisotropy of glacier ice (i.e. ice that deforms preferentially in certain modes and directions) at shear margins greatly facilitates streaming ice, however it is still poorly understood due to a lack of in-situ measurements and is usually incorporated into models as a simple scalar enhancement factor. The resurgence of polarimetric radar techniques to detect bulk fabric anisotropy through exploiting the birefringence of ice crystals has greatly aided quantification of the ice crystal orientation fabric (COF) across the Antarctic Ice Sheet. In our study, we invert these techniques to infer the azimuthal fabric strength at the Eastern Shear Margin of Thwaites Glacier from non-polarimetric airborne radargrams collected during the 2018-19 field season. From these results, we infer the evolution of the crystal orientation fabric across the shear margin, where ice is subjected to varying levels of both pure and simple shear. Our findings suggest the potential of the upper reaches of the ESM having undergone recent inward migration. Together with compatible ground-based polarimetric radar experiments, our study highlights the potential of radar sounding to observe and infer variations in fabric strength from regions of complex flow at multiple spatial scales. Because the bulk COF of ice sheets records the past history of ice sheet deformation and influences present-day ice flow dynamics, accurate measurements of ice fabric strength and orientation not only places constraints on present and past ice flow history, but also aids in the incorporation of anisotropic rheology in ice flow models.

How to cite: Young, T. J., Jordan, T. M., Martín, C., Schroeder, D. M., Christoffersen, P., Tulaczyk, S. M., Culberg, R., and Bienert, N. L.: Polarimetric radar-sounding to infer and quantify shear margin ice fabric anisotropy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2107, https://doi.org/10.5194/egusphere-egu21-2107, 2021.

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