HR: 14:55h
AN: C33D-06    [Abstracts]
TI: The Role of Plastic Necking in Ice Shelf Rifting: A Comparison with Lithospheric Rifts
AU: * Bassis, J N
EM: jbassis@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, San Diego, CA 92093-0225 United States
AU: Fricker, H A
EM: hafricker@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, San Diego, CA 92093-0225 United States
AU: Minster, J
EM: jbminster@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, San Diego, CA 92093-0225 United States
AB: Ice shelf rifts are through-cutting fractures that penetrate the entireice depth. Most treatments of rift propagation assume that the fractureprocess can be treated as brittle (i.e. ice is treated as an elasticmaterial and viscous effects are neglected). In this approach the riftis treated as a thin planar crack in the ice. However, over the timescales of rift propagation (years to decades), viscous strains exceedelastic strains by several orders of magnitude, making this aninappropriate assumption. We suggest that a more realistic formulationis to consider the rifting process as the result of strain localizationdue to plastic flow - sometimes called the "necking instability". Inthis theory deformation occurs in a zone with a characteristic lengthscale of several ice thicknesses rather than in an small zone around therift tip. Here we present the linear stability analysis which leads toplastic necking under plane strain conditions and determine theconditions where small perturbations in either the bottom profile orsurface profile of the ice shelf become amplified. The predictedsurface topography expected from a small initial thickness perturbationis compared with GLAS elevation profiles across ice shelf rifts, as wellas SRTM profiles across emerged rifts along tectonic plate boundaries.
DE: 9310 Antarctica
DE: 8109 Continental tectonics--extensional (0905)
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting