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

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.