Using specularity content to evaluate five geothermal heat flux maps of Totten Glacier

Abstract. Geothermal heat flux (GHF) is an important factor affecting the basal thermal environment of an ice sheet and crucial for its dynamics. But it is notoriously poorly defined for the Antarctic ice sheet. We compare basal thermal state of the Totten Glacier catchment as simulated by five different GHF datasets. We use a basal energy and water flow model coupled with a 3D full-Stokes ice dynamics model to estimate the basal temperature, basal friction heat and basal melting rate. In addition to the location of subglacial lakes, we use specularity content of the airborne radar returns as a two-sided constraint to discriminate between local wet or dry basal conditions and compare them with the basal state simulations with different GHF. Two medium magnitude GHF distribution maps derived from seismic modelling rank best at simulating both cold and warm bed regions well, the GHFs from Shen et al. (2020), and from Shapiro and Ritzwoller (2004). The best-fit simulated result shows that most of the inland bed area is frozen. Only the central inland subglacial canyon, co-located with high specularity content, reaches pressure-melting point consistently in all the five GHFs. Modelled basal melting rates there are generally 0–5 mm yr⁻¹ but with local maxima of 10 mm yr⁻¹. The fast-flowing grounded glaciers close to Totten ice shelf are lubricating their bases with melt water at rates of 10–400 mm yr⁻¹.