Ice stream basal conditions from block-wise surface data inversion and simple regression models of ice stream flow: Application to Bindschadler Ice Stream

Widespread basal conditions controlling ice stream flows are still beyond the scope of direct observation, thus knowledge of their magnitudes and variabilities comes from inversion of surface measurements: ice velocities, surface elevations, and thicknesses. We present a new approach to implement a widely accepted inverse method on regular (10 × 10 km) blocks, smaller than the whole domain, to enhance the spatial resolution of calculated basal conditions. Inverted basal friction coefficients and calculated shear stress have sharp transitions and large variations in small areas. Overall, the obtained basal shear stress is very small in regions of fast flowing ice. The results of the inversion, along with the surface variables, are used to construct two simple regression models of Bindschadler Ice Stream (former Ice Stream D) that reproduce 96% of observed velocity variations. While highly idealized, these regression models are sufficiently informative to be considered as parameterizations for ice stream flow in large-scale ice sheet models which lack the spatial and temporal resolution necessary to simulate ice stream dynamics in detail.