Distinct Groundwater Regimes in West Antarctic Sedimentary Basins Inferred From Magnetotelluric Imaging

Subglacial sedimentary basins in Antarctica are hypothesized to modulate ice flow and biogeochemical cycles via groundwater and geothermal feedbacks, yet their properties remain poorly constrained. Here, we present a joint quantitative analysis of new magnetotelluric (MT) data acquired at Thwaites Glacier (TG) and WAIS Divide, alongside legacy data sets from Whillans Ice Stream, Ross Ice Shelf, and South Pole. The new MT data reveal a shallow 1-D crustal structure, around the ice bed interface, at TG, overlying deeper 3-D structures. Our constrained 1-D transdimensional Bayesian inversion of the upper crust highlights that the sedimentary basin beneath TG exhibits relatively high resistivity (>10 Ωm), distinct from the lower-resistivity (<10 Ωm) basins at other sites. Sensitivity analysis reveals that the TG basin is horizontally heterogeneous, with conductive signatures in thicker sections and resistive signatures at GHOST Ridge, a subglacial topographic high which has been identified as a potential future stabilizing point. Conversely, basins beneath Subglacial Lake Whillans and the South Pole exhibit vertical stratification, with relatively resistive upper layers, up to 600 m thick, above conductive deeper layers (<5 Ωm). We hypothesize that complex, spatially variable groundwater regimes are widespread in Antarctica. These contrasting hydrological environments imply continent-scale variability in subglacial thermodynamics and possible modulation of inherent ice dynamics.