Dynamic jamming of iceberg-choked fjords

TL;DR

This study analyzes ice mélange dynamics during calving events at Jakobshavn Isbre6, revealing rapid jamming front propagation, energy dissipation, and the influence of jamming on ice stress transmission.

Contribution

It provides new insights into the rapid propagation of jamming fronts and the role of jamming in ice me9lange dynamics during calving.

Findings

Jamming front propagates faster than individual iceberg motion.

Ice me9lange undergoes initial compaction and slow relaxation.

Ice me9lange is nearly jammed during quiescent periods.

Abstract

We investigate the dynamics of ice m\'elange by analyzing rapid motion recorded by a time-lapse camera and terrestrial radar during several calving events that occurred at Jakobshavn Isbr\ae, Greenland. During calving events (1) the kinetic energy of the ice m\'elange is two orders of magnitude smaller than the total energy released during the events, (2) a jamming front propagates through the ice m\'elange at a rate that is an order of magnitude faster than the motion of individual icebergs, (3) the ice m\'elange undergoes initial compaction followed by slow relaxation and extension, and (4) motion of the ice m\'elange gradually decays before coming to an abrupt halt. These observations indicate that the ice m\'elange 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 m\'elange dynamics and stress transmission.