Data For: Seawater intrusion at the grounding line of Jakobshavn Isbrae, Greenland, from Terrestrial Radar Interferometry (TRI)

• Main Authors: Kim, Jae Hun, Rignot, Eric, Holland, David, Holland, Denise
• Format: Dataset
• Language: unknown
• Published: 2023
• Subjects: Jakobshavn Isbrae; Terrestrial radar interferometry; Grounding Line; Greenland; glacier; Ice Shelf; Jakobshavn
• Online Access: https://zenodo.org/record/8327432; https://doi.org/10.5061/dryad.1c59zw423

Jakobshavn Isbrae is a major outlet glacier in West Greenland that lost its protective ice shelf in 2002 and has been speeding up and retreating since. We image its grounding line for the first time with a ground portable radar interferometer deployed in 2016 and detect its migration at tidal frequencies. The southern half of the glacier develops a floating section (3 km x 3 km) that migrates in phase with the tide up to a distance of 1.5 km, which is far more than expected from flotation. We attribute the migration to kilometer-scale seawater intrusions, 10-20 cm in height, occurring at high tide. The intrusions reveal that the glacier bed must be 100-600 m deeper than expected on the south side, which illustrates that our knowledge of bed topography remains limited in this sector. We expect seawater intrusions to cause rapid melt of basal ice and play a major role in the glacier evolution. Funding provided by: University of California, IrvineCrossref Funder Registry ID: http://dx.doi.org/10.13039/100008476Award Number: Funding provided by: National Aeronautics and Space AdministrationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000104Award Number: 80NSSC21K1620 The GPRI complex images in slant-range geometry were combined to generate interferograms and geocoded into an Earth-fixed grid. The pointing angle of the GPRI was refined by adjusting image features in the geocoded datga with a reference Landsat image. Phase unwrapping was conducted from a stationary point on the glacier side margin. Here, we form interferograms using data acquired 16-minutes apart and we difference tthe interferograms every 6 hours. We extend the analysis over a period of 2 weeks. From the differential interferograms, we locate the transition boundary where the ice surface is first displaced vertically, or first fringe of displacement, which is our proxy for the grounding line. By repeating the exercise over time, we measure how the grounding line migrates back and forth with tide.