New aeromagnetic anomaly compilations help unveil regional-scale Antarctic subglacial geothermal heat flux heterogeneity

A new continent-wide aeromagnetic anomaly compilation for Antarctica, conformed at longer wavelengths with SWARM satellite magnetic data includes recent international datasets collected after the ADMAP 2.0 compilation analysed within the 3D Earth project of ESA.

This ADMAP 2.0+ product includes: 1) ROSETTA data collected by a US-NZ team over the Ross Ice Shelf; 2) reprocessed US-German and UK data collected over the Amundsen Sea Embayment; 3) German, Danish, UK- Argentina-Norwegian data over the Recovery ice stream catchment; 4) ESA PolarGAP data over South Pole and 5) enhanced vintage datasets for the Gamburtsev Subglacial Mountains and Wilkes and Dome C regions in East Antarctica. A new digital database was assembled using updated line data holdings and all data were levelled. microlevelled and stitched together via grid stitching approaches and subsequently differentially continued to 4 km and re-gridded on a 4 km grid mesh.

Here we use this new aeromagnetic anomaly compilation to re-assess Antarctic geothermal heat flux (GHF) heterogeneity, a critical basal boundary condition that influences Antarctic ice sheet flow and subglacial melting patterns and hydrology, and is related to crustal and lithospheric structure, composition, and heat production.

Within the 4D Antarctica ESA project we applied Curie Depth Point (CDP) estimation using the centroid, modified centroid and fractal/defractal approaches. Our new CDP map reveals regions of enhanced GHF along the coast of the Amundsen Sea Embayment, in agreement with independent seismological estimates. Potential thermal anomalies within the West Antarctic Rift System (WARS) also underlie the Byrd Subglacial Basin. Linear rift related anomalies are now imaged more clearly beneath the Siple Coast ice streams and active subglacial lake districts.

In East Antarctica, the new CDP estimates over the enigmatic WSB are significantly deeper compared even to the coldest sectors of the WARS. This suggests that if Mesozoic to Cenozoic extension affected this region, it mostly occurred at upper crustal levels rather than the whole lithosphere, in general agreement with relatively sparse seismological evidence for a predominantly cratonic lithospheric environment. A particularly intriguing region of enhanced GHF is identified in Dronning Maud Land. We propose that this could arise from lithospheric thinning perhaps associated with delamination processes, which have been independently inferred from petrological signatures in post-orogenic granitoids, emplaced after the pan-African age assembly of Gondwana. Alternatively, this feature could reflect thermal anomalies related to much later passive margin formation during Gondwana rifting and break up.

Finally, we discuss intriguing GHF anomalies inferred in the Dome C and Dome A subglacial lake regions in interior East Antarctica. We suggest the hypothesis that these anomalies relate to anomalously high intracrustal heat production, such as observed in Australia in some Proterozoic terranes, or to ill-constrained reactivation of the inherited structural architecture, This includes major Proterozoic and younger Pan-African age orogenic belts that may have been reactivated in response to far field stresses during Mesozoic to Cenozoic Gondwana break up and subsequent sea floor spreading processes.