This study uses a novel approach to extract information on the subglacial system, one of the least observed regions on our planet. The central idea is to combine satellite-derived information on ice-flow velocities with numerical models of subglacial conditions, and then test the results against seismic observations. In this way, the study introduces a direct, testable link between model predictions of effective pressure and independent constraints derived from seismic acoustic impedance data. This conceptually significant step forward advances our ability to constrain basal conditions of ice streams.