Quantifying temperature-sliding inconsistency in thermomechanical coupling: a comparative analysis of geothermal heat flux datasets at Totten Glacier

Abstract

Rapid sliding of ice sheets requires warm basal temperatures and lubricating basal meltwater, whereas slow velocities typically correlate with a frozen bed. However, ice sheet models often infer basal sliding by inverting surface velocity observations with the vertical structure of temperature and hence rheology held constant. If the inversion is allowed to freely vary sliding over the model domain, then inconsistencies between the basal thermal state and ice motion can arise lowering simulation realism. In this study, we propose a new method that quantifies inconsistencies when inferring thawed and frozen-bedded regions of ice sheets. This method can be used to evaluate the quality of ice sheet simulation results without requiring any englacial or subglacial measurements. We apply the method to evaluate simulation results for Totten Glacier using an isotropic 3D full-Stokes ice sheet model with eight geothermal heat flux (GHF) datasets and compare our evaluation results with inferences on basal thermal state from radar specularity. The rankings of GHF datasets based on inconsistency are closely aligned with those using the independent specularity content data. To illustrate the method's utility, we identified an overcooling inconsistency across all GHFs near the western boundary of Totten Glacier (70–72° S), a region with a bedrock canyon and fast surface ice velocities, suggesting that all GHFs are underestimated. Conversely, an overheating inconsistency exists in eastern Totten Glacier across all GHFs, indicating an overestimation of ice temperature that, in this case, is associated with a warm bias in surface temperature. Our approach opens a new avenue for assessing the self-consistency and reliability of ice sheet model results and GHF datasets, which may be widely applicable.