ANTARCTIC ICE SHEET AND SOLID EARTH INTERACTIONS: IMPLICATIONS FOR MANTLE VISCOSITY INFERENCES AND WEST ANTARCTIC VOLCANISM (Invited Presentation)

Understanding Antarctica’s past and future ice dynamics critically depends on our ability to accurately model the solid Earth’s response beneath the ice sheet to the surface mass loading. This response strongly depends on the assumed mantle rheology and ice loading history, both of which are highly uncertain. Antarctica is a region of limited observational constraints and complex 3D Earth structure: East Antarctica is characterized by a thick (~200 km) lithosphere overlying an upper mantle with a viscosity typical of cratons, 10²⁰-10²¹ Pa s, and, in contrast, beneath the volcanically active West Antarctic Rift System, the lithosphere thins to ~70 km and the viscosity within the shallow mantle may be as low as ~10¹⁸ Pa s. Here, we investigate how West Antarctica’s 3D mantle structure affects the isostatic adjustment to modern and paleo ice loading, including its impact on the use of geodetic observations, such as those made by GNSS, to provide constraints on the mantle viscosity. Our high-resolution finite volume modeling incorporates 3D Earth structure inferred from seismic tomography and we contrast these results with those made by simpler, 1D models. We further explore the implications this structure has on sea-level changes as well as the hydrostatic conditions that pace West Antarctic volcanism.