Dated radar Internal Reflection Horizons (IRHs) from the Wilkes Subglacial Basin (East Antarctica) for ice-sheet model calibration (v2.0)

2025 Wilkes Subglacial Basin Isochrones (v2.0)

This dataset is for all isochrones of age: 6.6 ± 0.1 ka, 13.1 ± 0.3 ka, 37.7 ± 0.5 ka, 64.1 ± 2.5 ka, 73.1 ± 1.2 ka, 90.8 ± 1.4 ka, 117.0 ± 1.3 ka, 122.8 ± 1.0 ka, and 128.4 ± 3.6 ka.

Please note: an error in the use of the version of the AICC chronology was detected during the reviews of the paper. This led to the ages previously provided in the v1.0 dataset to change slightly. The updated (correct) ages are provided in this v.2.0. All files here have been updated to incorporate these changes.

Field 1: Longitude (decimal degrees; WGS-84 EPSG: 4326)
Field 2: Latitude (decimal degrees; WGS-84 EPSG: 4326)
Field 3: Polar Stereographic X coordinates (metres; EPSG: 3031)
Field 4: Polar Stereographic Y coordinates (metres; EPSG: 3031)
Field 5: Pixel number of the corresponding isochrone relative to the BAS PASIN system range and sampling interval (value for conversion to metres: 3.8295)
Field 6: Isochrone depth below the surface (set at 0) (metres; using firn corrections of 9.5 and 14.6 metres for IRHs dated at TALDICE and EDC respectively, and an electromagnetic wave speed in ice of 168.5e6 m/s)
Field 7: Isochrone age (in years before present) dated either via intersections with existing stratigraphies (see below) or directly by intersection with the age-depth profile at TALDICE and EDC ice cores
Field 8: Ice thickness (in metres) calculated from the surface and bedrock returns from the along-track radar or gridded product, with no firn correction added
Field 9: Surface elevation above sea level (in metres relative to the WGS-84 ellipsoid) from either the along-track radar dataset (usually using on-board LiDAR) or gridded product (relative to Field 14)
Field 10: Bedrock elevation above sea level (in metres relative to the WGS-84 ellipsoid) from either the along-track bedrock pick from radar or gridded product (relative to Field 14)
Field 11: Type of radar waveform (e.g., pulse or chirp) or name of institute who acquired the data onto which the corresponding isochrone was traced
Field 12: Name of flightline onto which the corresponding isochrone was traced (relative to Field 11)
Field 13: Name of ice core used to date the corresponding isochrone (either TALDICE or EDC), useful to determine the value for the firn correction used (relative to Field 6)
Field 14: Integer indicating whether the ice thickness, surface, and bed elevation data are from (1) the along-track radar or (2) the gridded Bedmap3 product (Pritchard et al., 2025, Sci. Data) (relative to Field 8 and 10 respectively)

Processing: Schlumberger Petrel (tracing) and MATLAB (data processing)

Support: University of Bern Oeschger Centre for Climate Change Research, British Antarctic Survey, Alfred-Wegener Institute, The University of Texas at Austin
Funding: Swiss National Science Foundation (SNSF) Starting Grant 2022 "Charting Antarctic Ice Sheet evolution via the ice sheet’s internal stratigraphy" (CHARIBDIS)

Personnel: Julien A. Bodart (julien.bodart@unibe.ch)
Personnel: Johannes C.R. Sutter (johannes.sutter@unibe.ch)

Length_of_header: 52 lines
Not_a_number: Missing values have been replaced by "NaN"
Data separator: The separator is a single space

Publication: Bodart et al., 2025 (in review; The Cryosphere; https://doi.org/10.5194/egusphere-2025-5381)

Isochrones were traced primarily on the British Antarctic Survey's PASIN radar system flown during the WISE-ISODYN 2005-06 survey over the Wilkes Subglacial Basin and with a direct connection between the EDC and TALDICE ice core sites. Additional airborne radar datasets were also used to provide additional tiepoints and enhance crossover density in sparse areas. These additional datasets include individual flights from CRESIS Operation IceBridge using the MCoRDS radar system, AWI using the EMR radar system, and UTIG using the HiCARS radar system.

The WISE-ISODYN data was acquired using the PASIN-1 radar system (centre frequency: 150 MHz; bandwidth: 20 MHz; sampling frequency: 22 MHz; sampling interval: 0.4545 ns), using a 0.1 μs pulse and a 4 μs, 10 MHz chirp simultaneously (abbreviated "_pL" and "_cL" respectively in the LINE_ID). Most of the radar data used in this study (except older AWI EMR data) were 2D SAR processed using advanced algorithms of different complexities. For more details on the radar processing methods used, please refer to Frémand et al. (2022, ESSD), CReSIS 2018 (manual), Nixdorf et al. (1999, An. Glac.), or Young et al. (2016, Phil. Trans. R. Soc. A). Further processing was also applied to the processed radar data to facilitate IRH tracing, including air-to-ice travel time removal (using LiDAR surface when available), surface alignment to 0, a custom gain function, and horizontal averaging to enhance englacial layering (Ashmore et al., 2020, GRL; Bodart et al., 2021, JGR-ES). These same steps were applied to all non-BAS radar datasets for consistency.

All radar datasets were then exported to SEGY files with a "dt" scalar of 0.001. The BAS PASIN files were first imported into Schlumberger Petrel with a sampling interval of 1, reflecting the range of the radar system from top to bottom (range: approximately 1200 samples). All non-BAS data were then adapted in Petrel to match the vertical scale of the BAS PASIN vertical axis so as to facilitate tracing and avoid vertical offsets between datasets.

The isochrones were dated using the AICC2023 chronology (Bouchet et al., 2023, CP) at intersections with TALDICE and EDC cores, or via intersection with published stratigraphies (Winter et al., 2019, TC; Cavitte et al., 2021, ESSD). 

Only isochrones traced as part of this project are included to avoid duplication with previously published work. An extra column in the dataset indicates where each data point was dated (either TALDICE or EDC).

The ice thickness, surface, and bed elevations values provided in this dataset come directly from the along-track radar, where possible. Where there are no data for the ice thickness, surface, or bed elevations, the values come from the gridded Bedmap3 data product (see Field 14 for source of elevation values).