Firn Velocity Structure from Distributed Acoustic Sensing on Thwaites Eastern Ice Shelf, Antarctica
Loading...
Authors
Dohm, Kayleigh
Issue Date
2025
Type
Thesis
Language
en_US
Keywords
Cryosphere , DAS , Firn , Refraction Microtremor , Seismology , Thwaites
Alternative Title
Abstract
This study presents a Distributed Acoustic Sensing (DAS) investigation of the firn structure on Thwaites Eastern Ice Shelf (TEIS), a critical and rapidly evolving region of the West Antarctic Ice Sheet. TEIS is vulnerable to both oceanic and atmospheric changes and thus has the potential to be one of the largest contributors to sea level rise. Given the accelerated thinning and anticipated detachment from its pinning point, understanding the structural integrity of TEIS is paramount for predicting the future stability of Thwaites Glacier. A 340-meter horizontal DAS experiment was deployed at the Automated Meteorology Ice Geophysics Observation System III station on TEIS as part of the International Thwaites Glacier Collaboration. Both active and passive seismic energy were recorded to develop 2D P- and S-wave velocity models of the firn column. These models aim to provide high-resolution estimates of firn depth and identify velocity heterogeneities indicative of variations in structural and physical properties, including potential ice lenses and melt features. The results demonstrate the efficacy of DAS in acquiring high-quality seismic data in the cryosphere. The derived velocity models generally agree with firn depths and velocities estimated with other geophysical techniques on Antarctic ice. The resulting S-wave velocity model constrains the pore closeoff depth to 45-55 m and shows the presence of sharp vertical velocity gradients. The P-wave model, with its higher sensitivity to fluid content, provides a more detailed view of potential heterogeneities, including an observed high-velocity anomaly. This study highlights the potential of DAS as a rapidly deployable method for characterizing 2D firn structure over large distances. This study contributes to a better understanding of the processes that may influence Thwaites’ stability and vulnerability to collapse.