The relationship between ice velocity and bed topography on Byrd Glacier, Antarctica

Bed topography controls the pattern and magnitude of ice velocity, far into the catchment basin of many Antarctic outlet glaciers. Predictive models of glacier dynamics and ice sheet mass balance rely on well-prescribed bed topography, but in many regions bed topography is largely unknown. This particular study investigates the relationship between bed and surface topography and ice velocity in the catchment basin and trunk of Byrd Glacier. Byrd Glacier drains ~19 % of the area of the East Antarctic Ice Sheet (1,070,400 km2), and has the potential to play a significant role in the ice sheet's total mass balance. In 2011/2012, the Center for Remote Sensing of Ice Sheets (CReSIS) collected airborne radar data over Byrd Glacier. These new measurements of bed topography, along with updated surface digital elevation models (DEMs) and basin-wide ice velocity maps, are used to investigate the flow dynamics of Byrd Glacier with improved accuracy. Surface DEMs are derived from new high-resolution WorldView imagery; ice velocity is derived from repeat visible imagery, coupled with InSAR results (Rignot et al., 2011). Results exhibit relatively smooth depressions surrounding the inferred subglacial lakes, ~200 km upflow of the grounding line on Byrd Glacier (Stearns et al., 2008). Downflow of the subglacial lakes is a complex pattern of hills and valleys as ice enters the glacier trunk. At the mouth of the trunk is a large overdeepening (~2500 m) that coincides with faster ice flow. We use along- and across-flow radar profiles to perform detailed comparisons of ice velocity, bed topography and surface topography throughout the Byrd Glacier region. Gridded products are used to complete an updated force balance assessment. These results provide us with a better understanding of Byrd Glacier's flow dynamics and sensitivity to external perturbations.