Polarimetric radar reveals the spatial distribution of ice fabric at domes in East Antarctica

• Main Authors: Ershadi, M. Reza, Drews, Reinhard, Martín, Carlos, Eisen, Olaf, Ritz, Catherine, Corr, Hugh, Christmann, Julia, Zeising, Ole, Humbert, Angelika, Mulvaney, Robert
• Format: Text
• Language: English
• Published: 2021
• Subjects: Antarctic; East Antarctica; Antarc*; Antarctica; ice core
• Online Access: https://doi.org/10.5194/tc-2020-370; https://tc.copernicus.org/preprints/tc-2020-370/

Ice crystals are mechanically and dielectrically anisotropic. They progressively align under cumulative deformation, forming an ice crystal orientation fabric that, in turn, impacts ice deformation. However, almost all the observations of fabric are from ice core analysis and its interplay with the flow is unclear. Here, we present a non-linear inverse approach that combines radar polarimetry with vertical changes in anisotropic reflection to extract, for the first time, the full orientation tensor. The orientation tensor is routinely used to synthesize fabric information and it is used in anisotropic ice flow models. We validate our approach at two Antarctic ice-core sites (EDC and EDML) in contrasting flow regimes. Spatial variability of ice-fabric characteristics in the dome-to-flank transition near Dome C is quantified with 20 more sites located along a 36 km long cross-section. Local horizontal anisotropy increases under the dome summit and decreases away from the dome summit. We suggest that this is a consequence of the non-linear rheology of ice also known as Raymond effect. On larger spatial scales, horizontal anisotropy increases with increasing distance from the dome. At most of the sites, the main driver of ice-fabric evolution is vertical compression, yet our data show that ice fabric horizontal distribution is consistent with the present horizontal flow. Our method, which uses co- and cross polarimetric radar data suitable for profiling radar applications, can constrain ice-fabric distribution on a spatial scale comparable to ice flow observations and models.