The Beardmore Basal Body: Tracing Basal Features of the Ross Ice Shelf

A persistent near-basal reflector was discovered in the ROSETTA-Ice Project's Shallow Ice Radar (SIR) dataset during an effort to comprehensively map the internal structure and different ice bodies contained within the Ross Ice Shelf. Further investigation into the basal feature successfully tracked it from the grounding line to the calving front, along the flow of the Beardmore Glacier ice stream - an expanse of ~547 km across the ice shelf. The feature was found in ~35 radargrams, and was identifiable due to its consistent distinct shape, stratigraphy, depth, and size across the surveyed ice. The upper bound of this feature has two main arches that contain its rainbow-like stratigraphy, most visible with high-contrast filtered images. At their peak, these arches sit at ~250m to 300m below the ice surface; and their edges intersect the basal reflector. This basal feature appears to be independent of the Continental Meteoric Ice (CMI) reflector associated with Beardmore Glacier. The CMI reflector is a shallow, bright horizon in the SIR dataset; which has been identified as the interface between grounded glacier ice flowing onto the floating ice shelf. The CMI reflector deepens as it moves downstream, which has been traced and measured to generate a history of surface accumulation, or Local Meteoric Ice (LMI), on the Ross Ice Shelf. This basal feature exhibits similar traits: shallower upstream, deeper downstream, and bright radar reflection in each frame. However, unlike the CMI reflector, the basal reflector is also sporadically visible in both the ROSETTA-Ice Project's Deep ICE (DICE) radar and Operation IceBridge (OIB) radargrams. In this presentation we compare present-day flow and mass balance with the along-flow evolution of this feature, termed the Beardmore Basal Body (BBB), to explore the internal structure and history of the Ross Ice Shelf.