Abstract:
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)
Keywords:
Antarctica, Curie depth point, Geothermal heat flow, Transantarctic Mountains, Wilkes Subglacial Basin, spectral analysis of magnetic data
Lowe, M., Mather, B., Green, C., Jordan, T., Ebbing, J., & Larter, R. (2022). Curie depth points and Geothermal heat flow estimates from spectral analysis of magnetic data in the Transantarctic Mountains and Wilkes Subglacial Basin region. (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/b8dcbaa9-3ac0-42bd-95a5-6b5961cbcb7e
| Use Constraints: | This data is covered by a UK Open Government Licence (http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/) Please cite this dataset as follows: Lowe, M., Mather, B., Green, C., Jordan, T., Ebbing, J., & Larter, R. (2022). Curie depth points and Geothermal heat flow estimates from spectral analysis of magnetic data in the Transantarctic Mountains and Wilkes Subglacial Basin region. (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/B8DCBAA9-3AC0-42BD-95A5-6B5961CBCB7E |
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| Creation Date: | 2022-09-15 |
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| Dataset Progress: | Complete |
| Dataset Language: | English |
| ISO Topic Categories: |
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| Parameters: |
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| Personnel: | |
| Name | PDC BAS |
| Role(s) | Metadata Author |
| Organisation | British Antarctic Survey |
| Name | Mr Maximilian Lowe |
| Role(s) | Investigator |
| Organisation | British Antarctic Survey |
| Name | Ben Mather |
| Role(s) | Investigator |
| Organisation | University of Sydney |
| Name | Dr Chris Green |
| Role(s) | Investigator |
| Organisation | University of Leeds |
| Name | Dr Tom Jordan |
| Role(s) | Investigator |
| Organisation | British Antarctic Survey |
| Name | Dr Jorg Ebbing |
| Role(s) | Investigator |
| Organisation | Christian-Albrechts-Universit?t zu Kiel |
| Name | Dr Robert D Larter |
| Role(s) | Investigator |
| Organisation | British Antarctic Survey |
| Parent Dataset: | N/A |
| Quality: | 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. | |
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| Lineage: | 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. |
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| Temporal Coverage: | |
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| Start Date | 2022-05-10 |
| End Date | 2022-05-12 |
| Spatial Coverage: | |
| Latitude | |
| Southernmost | -79.8 |
| Northernmost | -67.9 |
| Longitude | |
| Westernmost | 139 |
| Easternmost | 180 |
| Altitude | |
| Min Altitude | N/A |
| Max Altitude | N/A |
| Depth | |
| Min Depth | 13.2km |
| Max Depth | 37.8km |
| Data Resolution: | |
| Latitude Resolution | N/A |
| Longitude Resolution | N/A |
| Horizontal Resolution Range | 10 km - < 50 km or approximately .09 degree - < .5 degree |
| Vertical Resolution | N/A |
| Vertical Resolution Range | N/A |
| Temporal Resolution | N/A |
| Temporal Resolution Range | N/A |
| Location: | |
| Location | Antarctica |
| Detailed Location | Transantarctic Mountains |
| Location | Antarctica |
| Detailed Location | Wilkes Subglacial Basin |
| Data Collection: | 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. |
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| Distribution: | |
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| Distribution Media | Online Internet (HTTP) |
| Distribution Size | 55MB |
| Distribution Format | ASCII |
| Fees | N/A |
| Data Storage: | The results are presented in three csv files for each window size (200 by 200 km window, 300 by 300 km window and 400 by 400 km window). Each csv file contains the following 15 columns: Window_number: Describes the window form which the Power spectrum, CDP and GHF are calculated. Note that only windows are presented that passed the 80% threshold of data coverage. Therefore, the window number is not necessarily starting at 1. Lon: gives the centroid longitude for the given window. Lat: gives the centroid latitude for the given window. X_PS_m: gives the centroid location in polar stereographic projection in meter. Y_PS_m: gives the centroid location in polar stereographic projection in meter. CDP_sea_level_km: describes the Curie Depth Point for the given window relative to sea level in km. Positive axis down. CDP_bedrock_surface_km: describes the Curie Depth Point for the given window below the bedrock surface in km. Positive axis down. CDP_uncertainty_km: describes the uncertainty of the Curie depth point estimation in km. Positive axis down. GHF_mW/m^2: describes the geothermal heat flow for the given window in mW/m2. GHF_uncertainty_mW/m^2: describes the uncertainty of the estimated geothermal heat flow for the given window in mW/m2. Data_coverage_%: describes the percentage of magnetic data coverage for the given window. Intercept_zT: gives the intercept of the Top of the magnetic layer (zT) estimation in the medium wavenumber part of the power spectrum. Slope_zT: gives the slope of the Top of the magnetic layer (zT) estimation in the medium wavenumber part of the power spectrum. Intercept_z0: gives the intercept of the centroid depth of the magnetic layer (z0) estimation in the low wavenumber part of the power spectrum. Slope_z0: gives the slope of the centroid depth of the magnetic layer (z0) estimation in the low wavenumber part of the power spectrum. In addition, every power spectrum is published for every window configuration as xyz files (In total, 11 566 files). Each of the files contains two columns. Column one is the wavenumber K (x-axis) and column two is the amplitude of the power spectrum (y-axis). The wavenumber is defined for all windows as: |k|/(2π). The amplitude of the power spectrum is defined for the power spectrum as: ln(Φ_ΔT (|k|)^(1/2))/( 2π) and for the weighted power spectrum as: ln(Φ_ΔT (|k|)^(1/2)/|k|)/( 2π). All the power spectrums are published along the csv file containing the results for transparency and reproducibility. The fit of the linear regression for each power spectrum can be recreated by plotting the linear regression using the intercept and slope value for the specific window from the csv result file. |