Ice Speed Variation Driven by Tidal Currents near the Terminus of Jakobshavn Isbræ, Greenland, Observed with Terrestrial Radar Interferometry

The time-varying ice velocity field near the terminus of Jakobshavn Isbræ, Greenland was observed with a terrestrial radar interferometer (TRI) in three summer campaigns in 2012, 2015 and 2016. Analysis of the velocity field and its response to ocean tides suggests a narrow (up to 1 km) floating tongue in early June of 2015/2016, but no evidence of floating tongue by early August 2012. There is significant periodic glacier motion seen by the TRI in the terminal region that is forced by ocean tides. A simple model for the seasonal evolution of the terminal region includes loss of the floating tongue during the summer months, driven by calving and terminus undercutting from warm ocean water. Motion of the iceberg mélange in front of the calving face includes motion induced by tide rise and fall, as well as horizontal motion that may reflect tidally driven currents, or perhaps meltwater events that have a diurnal component.