Using temperature-sliding inconsistency to evaluate eight geothermal heat flux maps for Totten Glacier

Rapid ice sheet sliding requires warm basal temperatures and lubricating basal meltwater.  However, ice sheet models often constrain sliding by inverting surface velocity observations with the vertical structure of temperature and rheology held constant.  If the inversion is allowed to freely vary sliding, then this approach can lead to inconsistencies between the basal temperature and sliding fields. In this study, we propose a new method to quantify the inconsistency between a modelled ice temperature field and the ice velocity field obtained when that temperature field is used to constrain an inversion. This method can be used to evaluate the quality of a modelled temperature field without requiring any englacial or subglacial measurements. We use the method to evaluate simulation results for Totten Glacier using an isotropic 3D ice sheet model with eight geothermal heat flux (GHF) datasets and compare our results with inferences on basal thermal state from radar specularity. The rankings of GHF datasets based on internal inconsistency aligns closely with those using independent specularity content data. Moreover, the spatial distribution of overcooling inconsistency for all datasets shows insufficient GHF at the western boundary of Totten Glacier between 70°S-73°S, which is characterized by a bedrock canyon with fast basal ice velocity. The overheating inconsistency reveals that poorly performing GHF datasets tend to overestimate GHF in central Totten Glacier. Our approach opens a new avenue for assessing the reliability of ice sheet model results and GHF datasets, which may be widely applicable.