We present a new approach to account for the influence of subglacial topography on geothermal heat flux beneath the Greenland and Antarctic ice sheets. We first establish a simple empirical proportionality between local geothermal flux and topographic relief within a given radius, based on a synthesis of existing observations of these properties elsewhere on Earth. This analysis essentially yields a high-pass filter that can be readily applied to existing large-scale geothermal heat flux fields to render them consistent with known subglacial topography. This empirical approach avoids both the geometric limitations of existing analytic models and the complex boundary conditions required by numerical heat flow models, yet it also produces results that are consistent with both of those methods, for example, increased heat flux within valleys and decreased heat flux along ridges. Comparison with borehole-derived geothermal heat flux suggests that our topographic correction is also valid for non-ice-covered areas of Earth and that a borehole location uncertainty of >100 m can limit the value of its inferred heat flux. Ice-sheet-wide application of this approach indicates that the effect of local topography upon geothermal heat flux can be as important as choice of regional geothermal heat flux field across a small portion of Antarctica (2%) and a larger portion of Greenland (13%), where subglacial topography is best resolved. We suggest that spatial variability in geothermal heat flux due to topography is most consequential in slower-flowing portions of the ice sheets, where there is no frictional heating due to basal sliding. We conclude that studies of interactions between ice sheets and geothermal heat flux must consider the effect of subglacial topography at sub-kilometer horizontal scales.
- Programme Area 5: Nature and Climate