Slow‐slip events on the Whillans Ice Plain, Antarctica, described using rate‐and‐state friction as an ice stream sliding law

Autor: Bradley P. Lipovsky, Eric M. Dunham
Rok vydání: 2017
Předmět:
Zdroj: Journal of Geophysical Research: Earth Surface. 122:973-1003
ISSN: 2169-9011
2169-9003
DOI: 10.1002/2016jf004183
Popis: The Whillans Ice Plain (WIP), Antarctica, experiences twice-daily tidally modulated stick-slip cycles. Slip events last about 30 minutes, have sliding velocities as high as ∼0.5 mm/s (15 km/yr), and have total slip ∼0.5 m. Slip events tend to occur during falling ocean tide: just after high tide and just before low tide. To reproduce these characteristics, we use rate-and-state friction, which is commonly used to simulate tectonic faulting, as an ice stream sliding law. This framework describes the evolving strength of the ice-bed interface throughout stick-slip cycles. We present simulations that resolve the cross-stream dimension using a depth-integrated treatment of an elastic ice layer loaded by tides and steady ice inflow. Steady sliding with rate-weakening friction is conditionally stable with steady sliding occurring for sufficiently narrow ice streams relative to a nucleation length. Stick-slip cycles occur when the ice stream is wider than the nucleation length, or, equivalently, when effective pressures exceed a critical value. Ice streams barely wider than the nucleation length experience slow-slip events, and our simulations suggest that the WIP is in this slow-slip regime. Slip events on the WIP show a sense of propagation and we reproduce this behavior by introducing a rate-strengthening region in the center of the otherwise rate-weakening ice stream. If pore pressures are raised above a critical value, our simulations predict that the WIP would exhibit quasi-steady tidally modulated sliding as observed on other ice streams. This study validates rate-and-state friction as a sliding law to describe ice stream sliding styles.
Databáze: OpenAIRE
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