Thermal ’ice’-ostasy: using remote geophysical data to model Antarctic surface heat flow

Abstract

Antarctica is host to the world’s largest terrestrial ice sheets. Due to concerns about changing global climate and resultant sea level change, the thermal stability of the ice sheets is important, yet poorly understood. Geothermal heat flow in Antarctica is a vital geophysical parameter in understanding the stability and movement of the overlying ice sheets. Conventional heat flow methods have not been reliable as the ice sheets have hindered the accessibility of surface rocks. This, coupled with the cost associated with the remoteness and hostility of the environment, means little data has been collected. Thus, geothermal heat flow is estimated with geophysical proxies. In this study, the principles of compositional and thermal isostasy are utilised to estimate the geothermal heat flow of Antarctica. Elevation, seismic velocity and geochemical data have been used to construct isostatic models of the Antarctic ice sheets and crust; this allows for isolation of the thermal component of isostatic elevation. Modelled geothermal gradients, incorporating geochemical, magnetic and seismic data, are then used to calculate a modelled thermal elevation. The two thermal elevations are then compared and the heat flow from the thermal model is taken as the geothermal heat flow. The first pass of this model computes moderate discrepancies between modelled thermal elevations and calculates very high geothermal heat flow, with a continental average of 92 mW/m2. Despite this, broad geological trends observed in this model agree with existing geological and tectonic knowledge. The errors present are likely due to issues in the modelling of geothermal proxies and isostatic assumptions. Though these results are not ideal, this model was successful in execution and serves as a proof of concept for further thermal isostatic modelling. With further refinement of the geophysical proxies and integration of more data types, this model may serve as a starting point for more integrated remote geophysical modelling of the thermal properties of the Antarctic lithosphere.