Subglacial conditions at a sticky spot along Kamb Ice Stream, West Antarctica

We present the results of a seismic reflection experiment performed transverse to flow a few tens of
kilometers above the main trunk of Kamb Ice Stream, West Antarctica, where we image a basal high surrounded by
variable subglacial conditions. This high rises as much as 200 m above the surrounding bed, acting as a major
sticking point that resists fast flow. Application of the amplitude variation with offset (AVO) seismic technique has
highlighted regions of frozen sediments along our profile, suggesting that the ice stream is experiencing basal
freeze-on in the region. The bedrock high appears to be at least partially draped in sediment cover, with a
concentrated area of weak, dilatant till flanking one edge. This dilatant till is further dispersed along our profile,
though it does not possess enough continuity to maintain streaming ice conditions. These results support the
hypothesis that the ongoing shutdown of Kamb Ice Stream is due to a loss in continuous basal lubrication.