Constraining Basal Conditions of the Greenland Ice Sheet Using Rayleigh-Wave Ellipticity From Ambient Seismic Noise Records

The physical conditions at the base of the Greenland Ice Sheet (GrIS) fundamentally dictate ice dynamics and its response to climate change. However, due to the limited spatial coverage of ice-penetrating radar surveys and borehole drilling observations, as well as the heavy reliance of thermo-mechanical ice-flow models on prescribed parameters, the shallow internal structure of the ice sheet and its basal environment remain insufficiently. Seismology provides an opportunity to constrain the depth of the ice–bedrock interface through the characterization of subsurface shear-wave velocity (Vs) structures.The study area is located northeast of Kangerlussuaq in Southwest Greenland. Previous studies show that long-term seismic velocity variations in this region are minimal, limiting the ability to infer basal frozen or thawed conditions from temporal changes alone. In addition, most investigations of the basal thermal state of the GrIS have focused on central and northern Greenland, leaving Southwest Greenland relatively under-explored. Although three-dimensional thermomechanical ice-flow models consistently predict thawed basal conditions here, these results rely primarily on numerical simulations and indirect constraints, highlighting the need for independent seismological validation.To address this, we analyze continuous ambient seismic noise recorded by 80 temporary seismic stations deployed across the study area. We apply the degree of polarization–ellipticity (DOP-E) method to measure Rayleigh-wave ellipticity and invert for shallow Vs structures within the priori knowledge of ice properties by using the neighborhood algorithm.This study provides seismological constraints on the internal and basal conditions of the GrIS in Southwest Greenland that complement existing radar observations and thermodynamic models, thereby establishing a new observational framework for investigating basal material properties and ice-dynamic processes in this region.