Greenland basal water distribution from airborne radar sounding (2003-2014) ...

• Main Authors: Jordan, Thomas M, Williams, Christopher N, Schroeder, Dustin M, Martos, Yasmina M, Cooper, Michael A, Siegert, Martin J, Paden, John D, Huybrechts, Philippe, Bamber, Jonathan L
• Format: Dataset
• Language: English
• Published: PANGAEA 2018
• Subjects: DATE/TIME; File content; File name; File format; File size; Uniform resource locator/link to file; Greenland; Ice Sheet
• Online Access: https://dx.doi.org/10.1594/pangaea.893097; https://doi.pangaea.de/10.1594/PANGAEA.893097

There is widespread, but often indirect, evidence that a significant fraction of the bed beneath the Greenland Ice Sheet is thawed (at or above the pressure melting point for ice). This includes the beds of major outlet glaciers and their tributaries and a large area around the NorthGRIP borehole in the ice-sheet interior. The ice-sheet scale distribution of basal water is, however, poorly constrained by existing observations. In principle, airborne radio-echo sounding (RES) enables the detection of basal water from bed-echo reflectivity, but unambiguous mapping is limited by uncertainty in signal attenuation within the ice. Here we introduce a new, RES diagnostic for basal water that is associated with wet-dry transitions in bed material: bed-echo reflectivity variability. This technique acts as a form of edge detector and is a sufficient, but not necessary, criteria for basal water. However, the technique has the advantage of being attenuation-insensitive and suited to data combination enabling combined ... : The basal water distribution is derived from the ACORDS, MCRDS and MCoRDS airborne radar sensors over 13 field seasons from 2003-2014. The flight-track data is provided as csv files on a season-by-season basis and for the full (13 season) data set. The data columns correspond to: (A) latitude, (B) longitude, (C) water binary value, at a 1 km along-track posting. The water binary value corresponds to: 1 == a 5 km bin with water detected, 0 == a 5 km bin with no water detected, NaN == a 5 km bin with no coverage.The basal water predictions are shown in Figures 7-10 of Jordan et al. 2018 and correspond to a subset of flight-track data where basal water is present: specifically, where there are rapid horizontal gradients in the bed dielectric (wet/dry transitions). The predictions therefore act as a sufficient constraint upon the basal water distribution rather than being a fully comprehensive flight-track map for basal water extent. ...