Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 115, Issue 20, Pages 5105-5110Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1715136115
Keywords
jamming; granular; glacier; melange; calving
Categories
Funding
- National Science Foundation [DMR-1506446, DMR-1506991, DMR-1506307]
- NASA Earth and Space Fellowship [NNX14AL29H]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1506307] Funding Source: National Science Foundation
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Tidewater glacier fjords are often filled with a collection of calved icebergs, brash ice, and sea ice. For glaciers with high calving rates, this melange of ice can be jam-packed, so that the flow of ice fragments is mostly determined by granular interactions. In the jammed state, ice melange has been hypothesized to influence iceberg calving and capsize, dispersion and attenuation of ocean waves, injection of freshwater into fjords, and fjord circulation. However, detailed measurements of ice melange are lacking due to difficulties in instrumenting remote, ice-choked fjords. Here we characterize the flow and associated stress in ice melange, using a combination of terrestrial radar data, laboratory experiments, and numerical simulations. We find that, during periods of terminus quiescence, ice melange experiences laminar flow over timescales of hours to days. The uniform flow fields are bounded by shear margins along fjord walls where force chains between granular icebergs terminate. In addition, the average force per unit width that is transmitted to the glacier terminus, which can exceed 10(7) N/m, increases exponentially with the melange length-to-width ratio. These buttressing forces are sufficiently high to inhibit the initiation of large-scale calving events, supporting the notion that ice melange can be viewed as a weak granular ice shelf that transmits stresses from fjord walls back to glacier termini.
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