Investigating fabric signatures in the South Pole - Dome A sector, Antarctica

The uniaxial crystalline symmetry of an ice crystal gives rise to anisotropy in its electrical and mechanical behavior. Deformation of polycrystalline ice leads to preferential enhancement of these properties in certain orientations which constitutes fabric. These fabric regimes can be used as a metric for assessing compressional or tensional stresses in an ice sheet. The bulk mechanical anisotropy can be inferred based on the phenomenon of birefringence (1) (the splitting of a propagating wave through anisotropic media) observed in along-track radar return profiles.

 

The exploration of the South Pole subglacial basin and Dome A region undertaken by the NSF Center for Oldest Ice Exploration (COLDEX) during 2022-24 has presented a unique opportunity to analyze birefringence systematically and test the hypothesis of enhanced ice flow in the past (2). Fossil fast flow leads to a distinct fabric formation that can be discerned through the systematic analysis of birefringence induced banding and anisotropy induced bulk dielectric permittivity offsets in different acquisition configurations. We present a preliminary analysis of these signatures and place them in the context of paleo ice flow in the region. 

 

(1) Hargreaves, N. D. (1977). The polarization of radio signals in the radio echo sounding of ice sheets. Journal of Physics D: Applied Physics, 10(9), 1285–1304. https://doi.org/10.1088/0022-3727/10/9/012 

(2) Bingham, R. G., M. J. Siegert, D. A. Young, and D. D. Blankenship (2007), Organized flow from the South Pole to the Filchner-Ronne ice shelf: An assessment of balance velocities in interior East Antarctica using radio echo sounding data, J. Geophys. Res., 112, F03S26, doi:10.1029/2006JF000556.