Indication of a dilatant bed near Downstream B Camp, Ice Stream B, Antarctica

Phases of seismic P-wave reflections from the bed of Ice Stream B ata site on its ice plain have been examined. The survey comprised a 36 km line at ashallow angle (18°) to ice movement and four 3.6 km cross lines. Reversed-phase and unreversed-phase reflections each characterize about half the bed. The corresponding zones can be correlated in stripes quasi-parallel to ice movement. We take this as support for a model previously developed that relates the zones to different types of subglacial sediment dragged along by the ice. There is also evidence for patches of pooled water.