Modification of Antarctic geothermal heat flux by groundwater flow

Gabriel Cairns , Graham Benham, Ian Hewitt

The geothermal heat flux to the bed of the ice in Antarctica is important for ice flow and basal meltwater production, but is also highly uncertain. In particular, it is thought that groundwater flow in sedimentary basins could modify the geothermal heat flux to the ice bed by advecting heat, but this process is unaccounted for in current models. In this paper, we develop a mathematical model to investigate the effect of three-dimensional groundwater flow, driven by topography and sediment compaction, on subglacial heat transport. We then obtain a reduced-order approximate solution to this model. Using this approximate solution combined with geophysical data, we find that groundwater flow could enhance or reduce geothermal heat flux by tens of mW m-2 across large regions of Antarctica. We find that topographically-driven groundwater flow enhances heat flux in the centre of ice streams and reduces it at the margins, while compaction-driven groundwater flow enhances heat flux beneath thinning ice and reduces it beneath thickening ice. Our results provide insight into the possible effect of groundwater flow on Antarctic geothermal heat flux, and highlight the need for further investigation into the properties of Antarctic sedimentary basins.