Partitioning the geothermal component of basal melting beneath ice-sheets: lessons from Greenland

Winnie Chu1, Tom Jordan1,2, Yasmina Martos4,5, Dustin Schroeder1,3, Jonathan Bamber2

1Department of Geophysics, Stanford University , Stanford, United States, 2School of Geographical Sciences, University of Bristol, Bristol, United Kingdom, 3Department of Electrical Engineering, Stanford University , Stanford , United States, 4NASA Goddard Space Flight Center, Greenbelt, United States, 5University of Maryland, College Park, United States

Geothermal heat flux impacts meltwater production and ice motion at the base of ice sheets. However, additional to geothermal heating, frictional and deformational heat sources also contribute to melt the ice base. Recent studies in Greenland Ice Sheet implicate that geothermal heating related to ancient hotspot activities influences the distribution of present-day subglacial hydrology. However, these studies mostly rely on qualitative comparisons between basal water and heat flux models. Presently, it is unclear how much of the observed basal water is produced by geothermal heating and how much is strain or friction related. Here we combine ice-sheet modeling, basal water predictions from radar sounding analysis, and the most advance geothermal heat flux distribution to provide a quantitative assessment of the role of geothermal heat flux on basal water production. We examine the sensitivity of basal melting to variations in geothermal heat flux using a thermal enthalpy scheme in the NASA Ice Sheet System Model (ISSM). By coupling the thermal and stress balance modeling components, we partition the relative contribution of geothermal, frictional, and deformational heating on basal melting for different regions across Greenland. We also use an ice-sheet-wide constraint for basal water derived from variability in radar bed reflectivity as an independent constraint to examine the model capabilities to produce basal melting. Together, our results reveal that the spatial distribution of elevated geothermal heat flux can explain the observed meltwater underneath vast regions of the Northern and Eastern ice-sheet interior. We discuss the implications of the presence of a stable melt production related to geothermal heating to the long-term dynamics and mass balance of the Greenland ice sheet. We also discuss how the approaches developed in Greenland could be adapted to further characterize the geothermal heat flux of the Antarctic Ice Sheet.

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