Inversion of Arctic Landfast Sea Ice Properties Using Distributed Acoustic Sensing on Ice

Arctic landfast sea ice is subject to mechanical forcing from winds, waves, currents, and interactions with drifting ice. However, the resulting wavefields and their effects on the mechanical properties of the ice remain difficult to characterize using existing in situ and remote-sensing observations due to limited spatial and temporal coverage. Distributed acoustic sensing (DAS) of fiber optic cable offers dense spatial sampling and continuous temporal coverage that can complement these approaches. We present the first DAS observations on Arctic landfast sea ice, using a 2-km-long armored fiber-optic cable installed at the snow-ice interface on ice near Utqiaġvik, Alaska for two weeks in spring 2025. The DAS recorded various signal types, including controlled hammer-generated signals and ambient flexural-gravity (FG) waves. We apply Bayesian dispersion-based inversions of the observed guided-wave modes to estimate ice properties. Hammer-generated waves yield estimates of Young's modulus and ice thickness of 5.4 GPa and 0.98 m, respectively; the inferred thickness agrees with independent field measurements. Directional beamforming of the L-shaped cable segment indicates a dominant FG-wave arrival direction from offshore with an effective Young's modulus of 0.6 GPa and compressive stress of 0.6 MPa. The lower effective modulus is consistent with previous reports of reduced effective moduli inferred from FG waves. The compressive stress shows a positive correlation with squared wind speed (r=0.37), indicating sensitivity to wind-related changes in the ambient wavefield. These results demonstrate that DAS can complement existing observations of sea-ice wavefields and mechanics, while highlighting the need to characterize its coupling and directional response.