Subglacial landscape formation and sediment discharge: relating basal conditions to bedform dimensions and properties at Rutford Ice Stream, West Antarctica

Basal conditions that facilitate fast ice flow are still poorly understood and their parameterization in ice-flow models results in high uncertainties in ice-flow and consequent sea-level rise projections. Direct observations of basal conditions beneath modern ice streams are limited due to the inaccessibility of the bed. One approach to understanding basal conditions is through investigating the basal landscape of ice streams and glaciers, which has been shaped by ice flow over the underlying substrate. Bedform variation together with observations of ice-flow properties can reveal glaciological and geological conditions present during bedform formation. Here we map the subglacial landscape and identify basal conditions of Rutford Ice Stream (West Antarctica) using different visualization techniques on novel high-resolution 3D radar data. This novel approach highlights small-scale features and details of bedforms that would otherwise be invisible in conventional radar grids. Our data reveal bedforms of <300 m in length, surrounded by bedforms of >10 km in length. We correlate variations in bedform dimensions and spacing to different glaciological and geological factors. We find no significant correlation between local (<3 × 3 km) variations in bedform dimensions and variations in ice-flow speed and (surface or basal) topography. We present a new model of subglacial sediment discharge, which proposes that variations in bedform dimensions are primarily driven by spatial variation in sediment properties and effective pressure. This work highlights the small-scale spatial variability of basal conditions and its implications for basal slip. This is critical for more reliable parameterization of basal friction of ice streams in numerical models.