Methodology:

Data presented here have been frequency filtered and 2D migrated (using a finite difference approach and migration velocity of 0.168 m ns-1), followed by the picking of the bed reflection using ReflexW software (Sandmeier Scientific Software). Reflectivity values were calculated following the method by Gades et al., (2000). The received power, presented in this dataset, is calculated within a 280 ns time window centred on, and encompassing, the bed reflection (Gades et al., 2000).

This received power has not been corrected for englacial attenuation. A calibration of the amplitude of this dataset using a control reflection point (e.g. where the dielectric contrast is known, such as at the ice-water interface at the base of an ice shelf) has not been possible here. The reflectivity within this data therefore only represents relative reflectivity.

Detailed information on how the reflectivity can be calibrated and analysed will be contained in Schlegel et al. (in prep.).

Data collection:

Instrumentation:

Surface radar data were acquired in 2016/17 (as part of the BEAMISH project), using the British Antarctic Survey (BAS) DELORES radar system (King et al., 2007). This system has a half-dipole length of 20 m, and radiates energy with a centre-frequency of ~3 MHz. Navigation along each line was provided by single-frequency GPS units mounted on the towing snowmobile. A sledge at the midpoint between receiver and transmitter was equipped with dual-frequency GPS receivers to provide more accurate positions for post-processing.

Software:

ReflexW (Sandmeier Scientific Software) as well as MATLAB for the calculation of the received power.

Data quality:

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 500 m spacing between them. The along track sampling is around 2 m. Data has been 2D migrated (along acquisition direction), the theoretical horizontal resolution of the dataset after 2D migration is 12 m.

The bed reflection was clearly identifiable along the whole dataset. The received power is calculated within a 280 ns time window centred on, and encompassing, the bed reflection (Gades et al., 2000).