High‐Resolution Characterization of the Firn Layer Near the West Antarctic Ice Sheet Divide Camp With Active and Passive Seismic Data

We construct a high-resolution shear-wave velocity (VS) model for the uppermost 100 m using ambient noise tomography near the West Antarctic Ice Sheet Divide camp. This is achieved via joint inversion of Rayleigh wave phase velocity and H/V ratio, whose signal-to-noise ratios are boosted by three-station interferometry and phase-matched filtering, respectively. The VS shows a steep increase (0.04–0.9 km/s) in the top 5 m, with sharp interfaces at ∼8–12 m, followed by a gradual increase (1.2–1.8 km/s) between 10 and 45 m depth, and to 2 km/s at ∼65 m. The compressional-wave velocity and empirically-obtained density profile compares well with the results from Herglotz–Wiechert inversion of diving waves in active-source shot experiments and ice core analysis. Our approach offers a tool to characterize high-resolution properties of the firn and shallow ice column, which helps to infer the physical properties of deeper ice sheets, thereby contributes to improved understanding of Earth's cryosphere.