We use polarimetric radar sounding to investigate variation in ice crystal orientation fabric within the near-surface (top 40-300 m) of Rutford Ice Stream, West Antarctica. To assess the influence of the fabric on ice flow, we use an analytical model to derive anisotropic enhancements of the flow law from the fabric measurements. In the shallowest ice (40-100 m) the azimuthal fabric orientation is consistent with flow-induced development and correlates with the surface strain field. Notably, toward the ice-stream margins, both the horizontal compression angle and fabric orientation tend toward 45 degrees relative to ice flow. This result is consistent with theoretical predictions of flow-induced fabric under simple shear, but to our knowledge has never been observed. The fabric orientation in deeper ice (100-300 m) is significantly misaligned with shallower ice in some locations, and therefore inconsistent with the local surface strain field. This result represents a new challenge for ice flow models which typically infer basal properties from the surface conditions assuming simplified vertical variation of ice flow. Our technique retrieves azimuthal variations in fabric but is insensitive to vertical variation, and we therefore constrain the fabric and rheology within two end-members: a vertical girdle or a horizontal pole. Our hypotheses are that fabric near the center of the ice-stream tends to a vertical girdle that enhances horizontal compression, and near the ice-stream margins tends to a horizontal pole that enhances lateral shear. ApRES radar data were collected as part of the BEAMISH Project (NERC AFI award numbers NE/G014159/1 and NE/G013187/1). Tom Jordan would like to acknowledge support from EU Horizon 2020 grant 747336-BRISRES-H2020-MSCA-IF-2016. ***** PLEASE BE ADVISED THIS DATA SET HAS BEEN RETRACTED ***** This data set had incorrect coordinates for one of the sites. In addition, some files were incorrectly labelled as belonging to one of the sites A new data set (see ''Related Data Set Metadata'' link below) addresses these issues and also includes significant additional data, as well as updated metadata and additional authors. Hence it is a wholly new data set, rather than an updated version of this data set. Please use this new data set instead.

A ground-based radar survey consisting of 35 discrete quad-polarization measurement sites over three field seasons was undertaken on Rutford Ice Stream, West Antarctica. Sites A01 to A10 were collected on 20 January 2017, along a profile orientated perpendicular to the ice flow direction. The 10 sites are located between the central ice flowline and the ice-stream margin along a profile of length 8.5 km with the inter-site spacing decreasing toward the ice-stream margin. Sites B01 to B10 were collected on 05 December 2019, along a profile orientated parallel to the central flowline. The sites were surveyed with the first site 4 km upstream of site A01 and the inter-site distance spacing fixed at 4 km. Sites C01 to C11 were collected on 14 December 2018, and located between sites A01 and A02 at 200 m spacing. Sites D01-D04, collected on 25 January 2019, are downstream of A01 and form a diamond shape with 800 m spacing. At each site, polarimetric radar-sounding measurements were made using an autonomous phase-sensitive radio-echo sounder (ApRES), a frequency-modulated continuous-wave radar. The ApRES has a centre frequency of 300 MHz and a bandwidth of 200 MHz, which results in a range resolution of approximately 40 cm in ice. ApRES radar data were collected as part of the BEAMISH Project (NERC AFI award numbers NE/G014159/1 and NE/G013187/1).

Seismic refraction data were acquired at two sites on Antarctica''s Larsen C Ice Shelf, in November 2017. The acquisition was performed to measure seismic anisotropy, a proxy for the stress condition, in the ice shelf following the calving of Iceberg A68 in July 2017. 2D seismic profiles were acquired at two sites: S1, close to the new calving front of the ice shelf, and S2, advected downstream from the site surveyed in the NERC funded project NE/E013414/1 (SOLIS). Profiles were rotated about a common midpoint to examine the variation in seismic properties with azimuth. Throughout, 24 geophones were deployed at 10 m offset, with data recorded at a Geometrics GEODE system; data are presented here in SEG-2 format. All acquisitions were performed by Dr Jim White (British Geological Survey) and Emma Pearce (University of Leeds, School of Earth and Environment), with support from BAS. The data is part of the NERC RACE project, NE/R012334/1.

Ground penetrating radar (GPR) data were acquired at a site on Antarctica''s Larsen C Ice Shelf, in November 2017. The acquisition was performed to measure radar anisotropy, a potential proxy for the stress condition in the upper ice shelf, following the calving of Iceberg A68 in July 2017. Two GPR common midpoint (CMP) gathers were acquired at Site S2, a site previously surveyed during the NERC funded NE/E013414/1 SOLIS project. These gathers were acquired first with GPR antennas extended in the flow-parallel direction (~ east), and then in the flow-orthogonal direction. The GPR system is a Sensors & Software pulseEKKO PRO, with 200 MHZ antennas. All acquisitions were performed by Dr Jim White (British Geological Survey) and Emma Pearce (University of Leeds, School of Earth and Environment), with support from BAS. The data is part of the NERC RACE project, NE/R012334/1.

Polarimetric phase-sensitive radar measurements were collected at the Western Antarctic Ice Sheet (WAIS) Divide on the 25th and 26th December 2019. The measurements were conducted at 10 sites along a 6 km-long transect ~5-10 km northeast of the location of the WAIS Divide Deep Ice Core. At each site, a suite of four quadrature (quad-) polarimetric measurements were collected using an autonomous phase-sensitive radio echo sounder (ApRES) in a single-input single-output (SISO) configuration. The study is part of the Thwaites Interdisciplinary Margin Evolution (TIME) project of the International Thwaites Glacier Collaboration (ITGC), and is a collaboration between the United States National Science Foundation (NSF) and the United Kingdom Natural Environment Research Council (NERC). It was funded by UK Natural Environment Research Council (NERC) research grant NE/S006788/1 and USA National Science Foundation (NSF) research grant 1739027.