Thermomechanical coupling shapes the Antarctic Ice Sheet’s internal structure

<title>Abstract</title> <p>The internal stratification and anisotropic structure of the Antarctic Ice Sheet (AIS) provide important information about current and future ice dynamics of the ice sheet, yet they remain poorly constrained. Here, we present the first continent-wide map of internal stratification and seismic anisotropy across the AIS, using the seismic data acquired since 1996. The AIS exhibits a spatially varying layered structure, characterized by an upper near-isotropic layer in the top approximately one-third of the ice thickness overlying a lower anisotropic ice column with the anisotropy axis tilted by approximately 30° from the vertical direction. The depth of the layer transition coincides with a cumulative vertical strain of ~0.4-0.8, consistent with the onset of dislocation creep. In the lower ice layer, the tilt of the anisotropic axis aligns with the direction of maximum surface compressional strain rate, indicating coupled deformation driven by vertical gravitational loading and lateral flow convergence; and the anisotropy magnitude increases with increasing basal temperature, suggesting enhanced intergranular water content in warmer ice. Ice dynamics of the AIS is thus controlled by internal transition of dislocation at depth, with the bottom layer influenced by variation of ice loading thickness, internal lateral flow, and varying intergranular water contents influenced by the basal temperature. This continent-scale framework of the AIS ice dynamics would be useful for advancing predictions of ice-sheet evolution and future sea-level rise.</p>