DOI: 10.5285/dbf2e081-b332-4d20-b242-2daa5fed25ae
title: Basal Elevation and Reflectivity beneath Rutford Ice Stream from ground-based 3D migrated radar data acquired in 2017/18 within two 3x3km2 areas

description: High-resolution basal topography and basal properties were calculated from two 3x3 km2 radar datasets acquired approximately 50 km upstream of the grounding line of Rutford Ice Stream in West Antarctica. The provided datasets contain several txt-files including the coordinates, two-way travel time of the bed reflection and the reflectivity of the bed reflection. The X and Y coordinates are projected in EPSG:3031 - WGS 84 / Antarctic Polar Stereographic coordinate system. Radar data were acquired between December 2017 and late January 2018 using the British Antarctic Survey's ground-based DELORES system as part of the BEAMISH project. Data acquisition and processing was compliant with 3D processing and migration. Radar data were frequency filtered and 3D migrated (using a 3D Kirchhoff Time Migration approach in SeisSpace/ProMAX (LGCHalliburton Software) and migration velocity of 0.168 m ns-1), followed by the picking of the bed reflection using Petrel (Schlumberger Software). For the interpretation of variation of bed properties, basal reflectivity was calculated as described in Schlegel et al., 2022 and Schlegel et al., 2024. 

This work was funded by NERC AFI award numbers NE/G014159/1, NE/G013187/1 and NE/F015879/1, and NERC National Capability Science: Strategic Research and Innovation Short Projects. Geophysical equipment was provided by NERC's Geophysical Equipment Facility, loan number 887. We thank BAS Operations and N. Gillett for fieldwork support and B. Craven for software support. University of Leeds acknowledges support of this work by Landmark Software and Services, a Landmark Company and use of SeisSpace/ProMAX via the Landmark University Grant Program, Agreements 2004-COM-024982, 2008-CON-010888 and subsequent renewals. The British Antarctic Survey acknowledges support of this work by Landmark Software and Services, a Landmark Company.
description: The dataset is composed of two 3*3km2 grids which were acquired in 2017/18. Spatial sampling is compatible with 3D migration (2 m along-track, 20 m across-track). Processing of the densely spaced grids includes regularisation of the acquisition grid by interpolation, bandpass filtering, correction for geometric spreading and 3D Kirchhoff Time migration (horizontal resolution of 24 m in both along- and cross-track directions).

3D topography: Data in both grids are compliant with 3D migration. For the application of the migration data were interpolated into a regular grid with regular line and trace spacing. Following this, data were frequency filtered and 3D migrated using a Kirchhoff Time migration approach (migration velocity of 0.168 m ns-1) in SeisSpace/ProMAX. The bed reflection was picked using a semi-automated 3D seeded picking algorithm in Petrel software (Landmark). The two-way traveltime of the bed reflection was then interpolated to a surface with 65 x 20 m cell size. 

Radar reflectivity: The amplitude of the reflection was corrected for englacial attenuation. Following this the bed reflectivity was calculated as described in Schlegel et al. (2022) (using a 280 ns window).
description: Instrumentation: Surface radar data were acquired using the British Antarctic Survey (BAS) DELORES radar system (King et al., 2007). Dual-frequency GPS antennas were mounted on the system for positioning.
description: The 3D migrated radar data shows more details of the bed topography compared to the 2D migrated data. Even though most parts of the bed show a clear reflection, the steep flanks of bedforms lack a clear return in the 3D migrated data.

The centre frequency of the DELORES dataset presented here is 3 MHz, the wavelength in ice (wave speed in ice=0.168 m ns-1) is 56 m. Lines were acquired perpendicular to the ice flow, with a 20 m spacing between them. The along-track sampling is around 2 m. Topography data has been 3D migrated, the theoretical horizontal resolution of the dataset after 3D migration is 12 m.