The Subglacial Melt Budget: Geothermal Heat as a Bounded Ice-Sheet Water Source

Geothermal heat at 40 to 70 mW/m2 reaching the beds of the Antarctic and Greenland ice sheets is converted to basal meltwater. The upper bound, if all geothermal heat went to melting, is 72.23 km3/yr for Antarctica (13.90 million km2, 764.5 GW at the central flux of 55 mW/m2) and 8.89 km3/yr for Greenland (1.71 million km2, 94.0 GW), a combined 81.12 km3/yr. Discounting for heat conducted into the ice (10 to 20 mW/m2) and for the fraction of the bed held at pressure melting (central 0.45 for Antarctica, 0.50 for Greenland) gives central terms of 23.64 km3/yr for Antarctica (bracket 9.19 to 43.34) and 3.23 km3/yr for Greenland (bracket 1.13 to 6.30). A pure-conduction grid bounds the thawed bed fraction at 0.70 (Antarctica) and 0.77 (Greenland) at central flux; advection holds the true fractions lower. The discounted Antarctic term is 23.64 per cent of adopted central surface-melt production and renews the inventoried Antarctic subglacial lake volume (14,000 km3) in 592 years; the Greenland term is 0.72 per cent of Greenland surface melt. All numbers are produced by the deposited compute.py. AI use is disclosed: drafting and computation assistance was provided by Dave, an AI system built and operated under the author's direction. The author, William Alexander Aldred, directed the work and is sole author of record.