Blocking a wave: frequency band gaps in ice shelves with periodic crevasses

• Main Authors: Freed-Brown, Julian, Amundson, Jason M., MacAyeal, Douglas R., Zhang, Wendy W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: International Glaciological Society 2012
• Subjects: glaciers; ice shelves; crevasses; elastic-flexural waves; band gaps; ocean wave/ice shelf interactions; ice shelf; Burton; Dorian; Annals of Glaciology; Ice Shelf; Ice Shelves
• Online Access: http://hdl.handle.net/11122/11016

We assess how the propagation of high-frequency elastic-flexural waves through an ice shelf is modified by the presence of spatially periodic crevasses. Analysis of the normal modes supported by the ice shelf with and without crevasses reveals that a periodic crevasse distribution qualitatively changes the mechanical response. We assess how the propagation of high-frequency elastic-flexural waves through an ice shelf is modified by the presence of spatially periodic crevasses. Analysis of the normal modes supported by the ice shelf with and without crevasses reveals that a periodic crevasse distribution qualitatively changes the mechanical response. The normal modes of an ice shelf free of crevasses are evenly distributed as a function of frequency. In contrast, the normal modes of a crevasse-ridden ice shelf are distributed unevenly. There are ‘band gaps’, frequency ranges over which no eigenmodes exist. A model ice shelf that is 50 km in lateral extent and 300 m thick with crevasses spaced 500 m apart has a band gap from 0.2 to 0.38 Hz. This is a frequency range relevant for ocean-wave/ice-shelf interactions. When the outermost edge of the crevassed ice shelf is oscillated at a frequency within the band gap, the ice shelf responds very differently from a crevasse-free ice shelf. The flexural motion of the crevassed ice shelf is confined to a small region near the outermost edge of the ice shelf and effectively ‘blocked’ from reaching the interior. We thank Dorian S. Abbot, Justin C. Burton, L. Mac Cathles IV, Nicholas Guttenberg and Sidney R. Nagel for encouragement and insightful feedback. This work is supported by the US National Science Foundation under grants ANT-0944193, OPP-0838811 and CMG-0934534. J.F-B. was supported by the Materials Research Science and Engineering Center at the University of Chicago (DMR- 0820054). Yes