DOI: 10.5281/zenodo.17348975
title: Dated radar Internal Reflection Horizons (IRHs) from Dronning Maud Land (East Antarctica) for ice-sheet model calibration

description: 2025 CHARISO (Dronning Maud Land) IsochronesThis dataset is for all isochrones of age: 4.8 ± 0.6, 7.4 ± 0.8, 25.6 ± 0.1, 38.1 ± 0.1, 52.2 ± 0.1, 73.4 ± 0.9, 91.0 ± 1.1Field 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 AWI Ultra-WideBand (UWB) narrowband system range and sampling interval (value for conversion to metres: 2.8167)Field 6: Isochrone depth below the surface (set at 0) (metres; using firn corrections of 13 and 15.5 metres for IRHs dated at EPICA Dronning Maud Land (EDML) and Dome Fuji (DF) respectively, and an electromagnetic wave speed in ice of 169.5e6 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 EDML or DF ice coresField 8: Ice thickness (in metres) calculated from the surface and bedrock returns from the along-track radar or gridded product, with no firn correction addedField 9: Surface elevation above sea level (in metres relative to the WGS-84 ellipsoid) from the REMA v2.0 dataset (Howat et al., 2019, TC) at a resolution of 10 metresField 10: Bedrock elevation above sea level (in metres relative to the WGS-84 ellipsoid) from either the combination of REMA surface elevation and along-track bedrock pick from radar or gridded product (relative to Field 14)Field 11: Type of radar waveform (e.g., narrowband or wideband) or name of institute who acquired the data onto which the corresponding isochrone was tracedField 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 EDML or DF), useful to determine the value for the firn correction used (relative to Field 6)Field 14: Integer indicating whether the ice thickness and bed elevations data are from (1) the along-track radar data 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 and Alfred-Wegener InstituteFunding: 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 linesNot_a_number: Missing values have been replaced by "NaN"Data separator: The separator is a single spacePublication: Bodart et al., 2025 (in review; The Cryosphere; https://doi.org/10.5194/egusphere-2025-5381)Isochrones were traced primarily on the Alfred-Wegener Institute UWB radar system flown during the CHARISO field seasons of 2023-24 and 2024-25 over Dronning Maud Land in narrowband mode (180-210 MHz range). Opportunistic airborne radar datasets were also used to provide additional tiepoints with existing isochrone stratigraphies and to expand the amount of crossovers in crossover-poor areas of the survey lines. These additional datasets include AWI UWB in wideband mode (150-520 MHz range / line 20231211_01) and the older AWI EMR system in the short-pulse mode (150 MHz / lines 19993136 and 20033141).The CHARISO data was acquired using the AWI UWB radar system in narrowband mode (centre frequency: 195 MHz; bandwidth: 30 MHz; sampling frequency: 160 MHz; sampling interval: 6.25 ns). Motion compensation, pulse compression, SAR focusing, and array processing were applied to the data (Franke et al., 2022, ESSD). Further processing was also applied to the processed radar data to facilitate IRH tracing, including the removal of the air-to-ice two-way travel time and the shifting of the ice surface to 0. The same processing steps were applied on all non-CHARISO radar lines mentioned above for consistency.All radar datasets were then exported to SEGY file format with a "dt" scalar parameter set to 0.001. The AWI UWB narrowband 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 1300 samples). All non-UWB narrowband radar products were then adapted in Petrel to match the vertical scale of the UWB narrowband vertical axis so as to facilitate tracing and avoid vertical offsets between datasets.The isochrones were dated primarily using intersections with an existing expansive IRH stratigraphy from Franke et al. (2025, TC), except for the second shallowest and the deepest isochrones in our dataset. The second-shallowest IRH is the lowest of the couplet identified by Franke et al. (2025), who dated the upper part of this couplet at 7.2 ka.The AICC2023 chronology (Bouchet et al., 2023, CP) was used to date this second-shallowest and deepest IRHs at EDML. Note that the deepest IRH was also traced and dated at DF ice core for comparison with EDML (Oyabu et al., 2023, CP).To avoid duplicates with Franke et al. (2025) and other IRH datasets in the region, this dataset only contains isochrones traced in the accompanying paper to this dataset. Please refer to the paper for more details on the tracing and dating methods. An extra column in the dataset indicates where each data point was dated (either EDML or DF), with EDML set to all isochrones dated previously by Franke et al. (2025).The ice thickness values provided in this dataset come directly from the along-track radar, where possible. Surface elevations come from the REMA v2.0 dataset. The bed elevations are obtained by subtracting ice thicknessfrom the along-track radar from REMA surface elevations. Where there are no ice thickness values, the ice thickness and bed elevations values come from the gridded Bedmap3 data product (see Field 14 for source of elevation values).