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

TL;DR

This study demonstrates that periodic crevasses in ice shelves create frequency band gaps that significantly alter wave propagation, confining flexural motion and potentially impacting ocean-ice interactions.

Contribution

It introduces a model showing how periodic crevasses induce band gaps in ice shelves, a novel insight into their mechanical response to high-frequency waves.

Findings

Band gaps occur between 0.2 and 0.38 Hz in crevassed ice shelves.

Flexural motion is confined near the edge when oscillated within a band gap.

Periodic crevasses qualitatively change the normal mode distribution.

Abstract

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.