The effect of bed topography on modeled grounding line migration in a conditional simulation of Thwaites Glacier, West Antarctica

Chief among the challenges involved with accurately modeling grounding line migration of marine terminating ice sheets is integrating grounding line dynamics together with accurate sub-kilometer scale bed topography. We address this challenge using a Berkeley Ice Sheet Initiative for Climate at Extreme Scales (BISICLES) ice sheet model with a new 250 m resolution conditional simulation of the bed beneath Thwaites Glacier and its catchment area. The new bed topography was created by interpolating aerogeophysical observations to a fine grid using inhomogeneous statistics with channelized morphology and a realistic small-scale roughness. The primary interest here is understanding how (and why) the more realistic bed geometry affects model behavior and projections of future change, relative to projections made using simpler bed geometries. We use the same forcing as prior work on the Thwaites and Pine Island Glacier systems--parameterized warm water incursion beneath the floating glacier terminus--and compare the resulting grounding line retreat to retreat simulated using the same model with a standard 1 km resolution basal elevation data set.