Dynamic jamming of iceberg-choked fjords

• Published in: Geophysical research letters Vol. 42; no. 4; pp. 1122 - 1129
• Main Authors: Peters, Ivo R., Amundson, Jason M., Cassotto, Ryan, Fahnestock, Mark, Darnell, Kristopher N., Truffer, Martin, Zhang, Wendy W.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 28.02.2015; John Wiley & Sons, Inc
• Subjects: calving; Cameras; Decay rate; Dynamic tests; Dynamics; Fjords; Geophysics; glaciers; icebergs; Jamming; Kinetic energy; Radar; Greenland, Vestgroenland, Jakobshavns Isbrae; AN, Greenland
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2014GL062715

We investigate the dynamics of ice mélange by analyzing rapid motion recorded by a time‐lapse camera and terrestrial radar during several calving events that occurred at Jakobshavn Isbræ, Greenland. During calving events (1) the kinetic energy of the ice mélange is 2 orders of magnitude smaller than the total energy released during the events, (2) a jamming front propagates through the ice mélange at a rate that is an order of magnitude faster than the motion of individual icebergs, (3) the ice mélange undergoes initial compaction followed by slow relaxation and extension, and (4) motion of the ice mélange gradually decays before coming to an abrupt halt. These observations indicate that the ice mélange experiences widespread jamming during calving events and is always close to being in a jammed state during periods of terminus quiescence. We therefore suspect that local jamming influences longer timescale ice mélange dynamics and stress transmission. Key Points Ice melange experiences widespread jamming during calving events The ice melange is closely packed during periods of terminus quiescence The kinetic energy of the melange is about 1% of the total released energy