DOI: 10.5285/b8dcbaa9-3ac0-42bd-95a5-6b5961cbcb7e
title: Curie depth points and Geothermal heat flow estimates from spectral analysis of magnetic data in the Transantarctic Mountains and Wilkes Subglacial Basin region.

description: We present Curie depth point (CDP) and geothermal heat flow (GHF) estimations based on spectral analysis of magnetic airborne data for the Transantarctic Mountains (TAM) and Wilkes Subglacial Basin area. The Curie depth point is defined as the depth at which the Curie Temperature of 580 degC is reached. The Curie Temperature describes the temperature at which magnetic minerals lose their ability to generate a strong magnetic field. We use exclusively high resolution magnetic airborne measurements from the ADMAP-2 compilation, where we have removed data with a 15 km blanking distance threshold to reported flight lines to minimise artefact from interpolation. The obtained magnetic dataset is upward continued to a constant station height of 4 km and subdivided into window with a window size of 200 km, 300 km, and 400 km. For each window we calculate the power spectrum and estimate the CDP from the power spectrum. Subsequently we estimate the magnetic data coverage for each window and discard CDP estimates for window below a data coverage threshold of 80%. From the CDP interface GHF is forward calculated assuming constant thermal conductivity for the crust and a constant temperature at the base of the ice sheet representing the pressure melting point. This study is motivated by the need of high resolution GHF models form the Icesheet modelling community especially in marine based Basins like the Wilkes Subglacial Basin as well as by interpretation of the origin of the Transantarctic Mountains. Recent seismic studies have argued that warmer west Antarctic is present beneath the Transantarctic Mountains, which give thermal support to the mountains range. This hypothesis should lead to increased GHF in the area and therefore can be tested against our GHF model. Our results show elevated heat flow in the area of the Transantarctic mountains supporting the idea of thermal support for the mountain range with an independent method. Furthermore, we image elevate heat flow in the central Basin of the Wilks Subglacial Basin and Rennick Graben which have not been imaged before by continent wide GHF models. Funding for this research was provided by NERC through a SENSE CDT studentship (NE/T00939X/1)
description: The Curie depth point (CDP) estimations are produces by spectral analysis of magnetic data. We used magnetic airborne measurements from the ADMAP 2 compilation, where we removed data with a 15 km blanking distance to reported flight line to limit interpolation. The magnetic data was then upward continued to a constant station height of 4 km, which is the maximum flight height of the ADMAP data in the area. The upward continued dataset is subdivided into window with a window sizes of 200 by 200 km, 300 by 300 km, and 400 by 400 km. The power spectrum for each window is calculated and the Curie depth point is estimated by fitting a linear regression to the corresponding parts of the power spectrum. The CDP is derived by: CDP = 2z0 - zT. Where z0 is the centroid depth of the magnetic layer and zT is the top of the magnetic layer. The centroid depth of the magnetic layer (z0) is calculated by estimating the slope of the first linear segment of the power spectrum, while the depth to the top of the magnetic layer (zT) is calculated by estimating the slope of the intermediate part of the power spectrum. In addition, the data coverage for each window is calculated. Windows with a data coverage of less then 80% are discarded and not presented in the results. Geothermal heat flow is forward calculated from the CDP using Fourier's law by assuming a constant thermal conductivity of 2.5 W/mK for the crust and a constant temperature of 0 degC at the bedrock interface corresponding to the pressure melting point. The reader is referred to the associated publication in JGR solid earth for an in-depth explanation of the applied methodology.
description: The power spectrum is calculated using the Python library Pycurious. The CDP and GHF estimations are performed using the following Python libraries SciPy learn, NumPy, Pandas. The magnetic data was upward continued at a constant station height using the Compudrape plug-in for Geosoft Oasis Montaj version 2021.2.
description: Uncertainty estimates of the CDP and GHF estimates are provided in the data files. The uncertainty for the CDP ranges from 2 km to 8 km throughout the study area. GHF uncertainties range from 2.9 mW/m2 to 48.8 mW/m2. In depth discussion on the uncertainty of the results are presented in the associated publication in JGR Solid Earth.