Insights into seismic anisotropy of temperate ice during simple shear deformation

• Main Authors: Llorens, Maria-Gema, Griera, Albert, Gomez-Rivas, Enrique, Bons, Paul D., Weikusat, Ilka, Prior, David J., Lebensohn, Ricardo
• Format: Conference Object
• Language: unknown
• Published: Computational Infrastructure for Geodynamics (CIG) 2020
• Subjects: Antarctic; Greenland; Antarc*
• Online Access: https://epic.awi.de/id/eprint/52729/; https://geodynamics.org/cig/events/calendar/2020-tectonics-workshop/; https://hdl.handle.net/10013/epic.3d768c03-65f1-4880-870f-c23300ffd887

The ice mass balances of Antarctic and Greenland ice sheets represent the largest uncertainty for predicting future sea-level rise. Understanding how ice flows from the accumulation to the ablation zone is therefore crucial for correctly estimating the changing mass in polar ice-sheets. On Earth, ice crystals have a hexagonal symmetry (ice lh) with a strong anisotropy favouring basal slip. This results in a progressive development of a vertical c-axis preferred orientation (LPO) of ice polycrystalline aggregates during deformation. In depth, the elastic anisotropy of polycrystalline ice gradually increases due the development of a vertical LPO. Observations of P-wave (Vp) and S-wave (Vs) velocities in ice sheets reveal a strong decrease of ~25% of Vs in depth, while Vp remains approximately constant. According to Wittlinger and Farra (2015) the low Vs may be due to the presence of unfrozen liquids resulting from pre-melting at grain joints and/or melting of chemical solutions buried in ice. Although previous studies of two-phase rocks (including melt and water) show that seismic velocities depend on both LPO and water content, studies on the effect of melt on polar ice seismic velocity are scarce. In this contribution we investigate the changes in P- and faster S-wave velocities during deformation of polycrystalline ice with different melt fractions.