New Curie depth estimates from satellite conformed aeromagnetic anomaly compilations and their implications for assessing Antarctic subglacial geothermal heat flux heterogeneity

Geothermal heat flux (GHF) is a critical basal boundary condition that exerts important influences on the initiation of flow of the Antarctic ice sheet and is related to crustal and lithospheric structure and composition. Despite its importance, our knowledge of Antarctic GHF heterogeneity remains limited and this hinders interdisciplinary efforts to better constrain Solid Earth influences on subglacial hydrology and ice sheet behaviour.

Within the framework of the 4D Antarctica ESA project we produced a new continent-wide aeromagnetic anomaly compilation for Antarctica, conformed at longer wavelengths with SWARM satellite magnetic data. It includes recent data collected after the ADMAP 2.0 compilation, over the Ross Ice Shelf, the Amundsen Sea Embayment and the Recovery and South Pole regions, as well as enhanced maps for the Gamburtsev Subglacial Mountains and Wilkes and Dome C regions, based on relevelling.

We applied Curie Depth Point (CDP) estimation using the centroid, modified centroid and fractal and defractal approaches. We tested different window sizes at continental scale and for detailed analysis (200x200 km; 300x300 km; 400x400 km) and centroid distances, and both automated ranges and hand-picked intervals over selected features. The estimates reveal regions of enhanced GHF along the coast of the Amundsen Sea Embayment, in general agreement with independent seismological estimates, and are interpreted as reflecting dynamic interactions between the West Antarctic Rift System and anomalously warm Pacific upper mantle at depth. A higher degree of continuity of potential thermal anomalies related to the Byrd Subglacial Basin is evident between the Thwaites and Pine Island catchments compared to a recent magnetic estimate (Dziadek et al., 2021). A large area of enhanced GHF under the Siple Coast ice streams and active subglacial lake districts is confirmed, but has lower values and greater complexity than previously imaged (Martos et al., 2017). This can be correlated with regions of thinner and thicker crust and different magnetic patterns as revealed from inversion of satellite and airborne gravity and aeromagnetic data respectively.

In East Antarctica, the new CDP estimates suggest that any Mesozoic to Cenozoic extension is restricted to upper crustal levels and is focussed in narrow regions. Intriguing, relatively shallow CDP anomalies (given their location within the composite East Antarctic craton) are revealed in the Dome C lake district and also Gamburtsev Subglacial Mountains lake district regions. These may speculatively stem either from intraplate Mesozoic to Cenozoic fault reactivation and/or enhanced intracrustal heat production. 

We conclude that our new Curie depth estimates yield geologically reasonable thermal boundary conditions, which can be used together with independent estimates derived e.g. from seismology, machine leaning and multi-variate analysis to initialise new thermal models that incorporate crust and lithosphere thickness variations and intracrustal composition (as a proxy for ranges of radiogenic heat production and thermal conductivity).