A Viscoelastic Model of Ice Stream Flow with Application to Stick-Slip Motion

Walker, R. T.; Parizek, B. R.; Alley, Richard B.; Nowicki, Sophie

doi:10.3389/feart.2016.00002

Cited by 9 publications

(7 citation statements)

References 35 publications

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“…Bindschadler et al [] proposed a simplified stick‐slip model where slip events occur when accumulated strain reaches a prescribed failure threshold. This model was refined to include the effects of viscosity [ Winberry et al , ; Goldberg et al , ] and expanded to higher spatial dimensions [ Sergienko et al , ; Walker et al , ]. However, weakening and unstable slip, in these studies, was an imposed consequence of reaching the failure threshold.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we conduct numerical simulations of ice stream sliding with rate‐and‐state friction. This study builds on previous models of WIP stick‐slip cycles [ Winberry et al , ; Sergienko et al , ; Goldberg et al , ; Walker et al , ] but explores the diversity of sliding styles that emerge with rate‐and‐state friction under various conditions. In the following, we first review observational constraints on the WIP events and then introduce the governing equations describing the elastic response of an ice stream with rate‐and‐state friction at its bed.…”

Section: Introductionmentioning

confidence: 99%

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

Lipovsky

Dunham

2017

JGR Earth Surface

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The Whillans Ice Plain (WIP), Antarctica, experiences twice daily tidally modulated stick‐slip cycles. Slip events last about 30 min, 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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Lipovsky

Dunham

2017

JGR Earth Surface

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“…Note the difference in colour scale between the two panels. Amplitudes and phases are taken from the circum-Antarctic inverse model (CATS2008a, which is an updated version of the inverse tide model described by Padman et al, 2002). to our understanding of the dynamics of its flow (Winberry et al, 2011(Winberry et al, , 2009Sergienko et al, 2009;Winberry et al, 2014;Walker et al, 2016). Nearby, the flow of Bindschadler Ice Stream responds differently, exhibiting smooth diurnal velocity fluctuations in response to the mainly diurnal vertical tides (Anandakrishnan et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Strong tidal variations in ice flow observed across the entire Ronne Ice Shelf and adjoining ice streams

Rosier¹,

Gudmundsson²,

King³

et al. 2017

Preprint

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Abstract. We present a compilation of GPS time series, including those for previously unpublished sites, showing that flow across the entire Ronne Ice Shelf and its adjoining ice streams is strongly affected by ocean tides. Previous observations have shown strong diurnal and semidiurnal motion of the ice shelf and surface flow speeds of Rutford Ice Stream (RIS) are known to vary with a fortnightly (Msf) periodicity. Our new dataset shows that the Msf flow modulation, first observed on RIS, is also found on Evans, Talutis, Institute and Foundation Ice Streams, i.e. on all ice streams for which data are available. The amplitude of the Msf signal increases downstream of grounding lines, reaching up to 20 % of mean flow speeds where ice streams feed into the main shelf. Upstream of ice stream grounding lines, decay length scales are relatively uniform for all ice streams but the speed at which the Msf signal propagates upstream shows more variation. Observations and modelling of tidal variations in ice flow can help constrain crucial parameters that determine the rate and extent of potential ice mass loss from Antarctica. Given that the Msf modulation in ice flow is readily observed across the entire region, at distances of up to 80 km upstream of grounding lines, but is not completely reproduced in any existing numerical model, this new dataset suggests a pressing need to identify the missing processes responsible for its generation and propagation. The new GPS data set is publicly available through the UKPDC at http://doi.org/10.5285/4fe11286-0e53-4a03-854c-a79a44d1e356.

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“…The likely explanation is that the WIS flow generates high shear stress on the sticky spot there, which lowers the hydropotential on the sticky spot and pumps lubricating water onto it, especially during the earthquakes that now enable most of the WIS motion (equivalent to the suction pump action at dilational fault jogs of tectonic earthquakes) [ Winberry et al , ; Luthra et al , ]. At present, slow‐moving KIS cannot similarly transfer stresses [ Walker et al , ] to drive large earthquakes that would pump water onto the sticky spot, but such behavior may have occurred in the past when KIS was active.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of the sticky spot of Kamb Ice Stream, West Antarctica

et al. 2017

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Amplitude analysis of reflection seismic data reveals the presence of highly variable bed conditions under the main sticky spot and adjacent regions of the Kamb Ice Stream (formerly ice stream C). The sticky spot, which is a zone of bed that imparts high basal resistance to ice flow, is situated on a local topographic high composed of consolidated sediments or sedimentary rock. Any meltwater draining from upglacier along the base of the ice is routed around the sticky spot. The ice over the sticky spot includes, in at least some places, a seismically detectable basal layer containing a low concentration of debris, which locally thickens to 40 m over a topographic low in the bed. The ice‐contact basal material ranges from dilated and highly porous to more‐compacted and stiff, and perhaps locally frozen. The softer material is preferentially in topographic lows, but there is not a one‐to‐one correspondence between basal character and basal topography. We speculate that the 40 m thick frozen‐on debris layer formed by glaciohydraulic supercooling of lake‐drainage events along a basal channel during the former, active phase of the ice stream. We also speculate that loss of lubricating water, perhaps from piracy upstream, contributed to the slowdown of the ice stream, with drag from the sticky spot playing an important role, and with the basal heterogeneity greatly increasing after the slowdown of the ice stream.

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A Viscoelastic Model of Ice Stream Flow with Application to Stick-Slip Motion

Cited by 9 publications

References 35 publications

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

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

Strong tidal variations in ice flow observed across the entire Ronne Ice Shelf and adjoining ice streams

Characteristics of the sticky spot of Kamb Ice Stream, West Antarctica

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