Comparing different methods for measurement of geothermal heat flux in East Antarctica

Abstract:

Estimating geothermal heat flux (GHF) at the base of the Antarctic Ice Sheet is essential for constraining numerical ice sheet models that will predict global sea level change. Several different methods can be used to obtain this information. One method relies on estimating the depth at which crustal rocks lose ferromagnetism, the Curie point depth (CPD). This method makes use of the large spatial coverage and detail of existing magnetic datasets such as the Antarctic Digital Magnetic Anomaly Project (ADMAP). The centroid spectral method has been extensively used to estimate the CPD for regional magnetic anomalies, wherein a radial power spectrum of magnetic data is analyzed over a certain window size to obtain estimates to the top and centroid of the magnetic anomaly, and thus the CPD. This information is then used to constrain a solution to the heat equation to obtain an accurate GHF measurement.

Another widely-used method is to analyze the amount of englacial layer drawdown in the ice as observed with ice-penetrating radar data. This method, based on that described in Jordan et al (2018), involves solving the 1-D advection equation to construct an age-depth curve constrained by observed or modelled accumulation and melt rates, and ice sheet rheology. The best-fitting curve is used to estimate the parameters at each point of layer downdraw along a radar transect, which is then used to constrain a solution to the heat equation for GHF.

We compare these two techniques applied to two areas of the East Antarctic Ice Sheet and consider where and why they disagree. Results from this research will help in evaluating the most effective method for GHF estimation in areas of deep ice, improving GHF estimates and, by extension, boundary conditions for models of ice sheet evolution. Furthermore, this research will improve the detection of thin-crust areas, thus allowing for better detection of rift zones and other tectonic features that are crucial in reconstructing the geological history of Antarctica.