DOI: 10.5285/f2de31af-9f83-44f8-9584-f0190a2cc3eb
title: Dated radar stratigraphy of the Pine Island Glacier catchment (West Antarctica) derived from BBAS-PASIN (2004-05) and OIB-MCoRDS2 (2016/2018) surveys

description: This dataset contains the position and depth of four spatially-extensive Internal Reflecting Horizons (or IRHs) traced on the British Antarctic Survey's PASIN system and NASA Operation IceBridge's MCoRDS2 system across the Pine Island Glacier catchment. Using the WAIS Divide ice-core chronology and a 1-D steady-state model, we assign ages to our four IRHs: (R1) 2.31-2.92 ka, (R2) 4.72 +/- 0.28 ka, (R3) 6.94 +/- 0.31 ka, and (R4) 16.50 +/- 0.79 ka.
description: Instrumentation and Processing: The main radar data is from the British Antarctic Survey's PASIN system, flown over Pine Island Glacier in the austral season 2004-05. Data were collected with two interleaved radar modes.The first was a deep-sounding, 150 MHz centre-frequency, 4-microseconds, 10 MHz chirp mode and the second was a 150 MHz, 0.1-microseconds pulse mode designed to image shallow IRHs but from which we are also able to recover IRHs deeper (~2 km) in the ice column. The second radar dataset used here is from NASA Operation IceBridge's MCoRDS2 system, flown in two separate surveys over Pine Island Glacier and nearby Thwaites and Institute Ice Stream catchments in 2016 and 2018. The system operated at a centre frequency of 190 MHz and a 50 MHz bandwidth. We used the CReSIS L1B standard products, produced with pulse compression, focused-SAR processing and along-track motion compensation. For the purposes of increasing IRH traceability on the PIG-PASIN data, we quadratically detrended each radar trace, normalised each pixel in a moving vertical window, and then applied a 10-trace horizontal average to reduce incoherent noise. For both the PIG-PASIN and the OIB-MCoRDS2 data, we removed the air-to-ice two-way travel time and shifted the surface elevation to time zero, prior to exporting the data to standard 2-D SEG-Y format for data interpretation. We conducted our IRH tracing in the Schlumberger Petrel 3-D seismic software using a semi-automated tracing algorithm that uses an adjustable window to track the local maxima of received reflected power between traces. Methodology and Results: We identified four prominent Internal Reflecting Horizons (or IRHs) that we term R1-4 in the PASIN and MCoRDS2 radar data. The upper three IRHs (R1-3) were chosen on the basis of high spatial continuity and high signal-to-noise ratio (SNR). We used available crossovers between radar profiles as calibration points to trace the IRHs and relied upon the distinctiveness of our IRHs when tracing between crossovers (see Bodart et al., 2021 for more details). We converted all our IRHs from time domain to depth using a value for the speed of electromagnetic waves through ice of 168.5 m/microseconds and applied a 10 m spatially-invariant firn correction. All our depth measurements are given in depth below the surface (set at 0 m). The maximum uncertainty for the IRHs traced on the PASIN data is +/- 17 m, and +/- 14 m on the IRHs traced on the MCoRDS2 data. More details on how these were calculated can be found in Bodart et al. (2021). The IRHs were dated using intersection with the WAIS divide ice-core and with the use of a steady-state 1-D vertical-strain model. Data Structure: Each CSV file contains six columns: (1) 'X' is the Cartesian x-coordinates in Polar Stereographic South (EPSG: 3031, -71 S) (units: meters). (2) 'Y' is the Cartesian y-coordinates in Polar Stereographic South (EPSG: 3031, -71 S) (units: meters). (3) 'Lon' is the longitudinal coordinate in WGS84 (EPSG: 4326) (units: degrees). (4) '''Lat' is the latitudinal coordinate in WGS84 (EPSG: 4326) (units: degrees). (5) 'Pick' is the pixel number below the ice surface of the radargram of that IRH. (6) 'Depth' is the depth of the IRH below the ice surface (units: meters). (7) 'RadarIceThick' is the ice thickness detected by the radar (units: meters). Missing values for radar ice thickness are shown as NaN. (8) 'FlightID' is the radar flight line number or segment. More information on the naming convention used for the CSVs can be found under 'Storage'.
description: BBAS/AGASEA PASIN survey: season 2004-05 NASA/OIB MCoRDS2 surveys: seasons 2016 and 2018
description: Uncertainties in IRH depths can be found in the Lineage section and in the paper. Missing values for radar ice thickness are shown as NaN.