Shear resistance and continuity of subglacial till: hydrology rules

AbstractThe field observations of G.S. Boulton stimulated widespread interest in deformable beds. Shear resistance of till in its critical state is insensitive to strain rate and increases linearly with effective pressure. During unsteady deformation, pseudo-viscous shear resistance can be caused by dilation of consolidated tills and resultant pore-pressure decline. This effect is probably uncommon, however, because susceptible tills of low hydraulic diffusivity are also those least likely to consolidate significantly during effective-pressure transients. Stick-slip motion at Whillans Ice Stream, Antarctica, indicates that its basal till must weaken during rapid slip and strengthen during longer periods of slower slip. Recurrence intervals for rapid-slip episodes there (6-18hours) indicate that till-strength variations, if driven by changes in pore pressure either related or unrelated to basal freezing, are focused in the uppermost several centimeters of the bed. Ploughing of grains at the bed surface and associated excess pore pressures in adjacent till can account for rate-weakening during rapid slip, with pore-pressure decay causing strengthening between slip episodes. By promoting shallow, sluggish subglacial water flow and low effective pressure, soft beds may help sustain themselves by slowing their own transport. Soft-bed shear resistance, kinematics and continuity are problems rooted in subglacial hydrology.

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Dynamics of stick–slip motion, Whillans Ice Stream, Antarctica

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2011.02.052 ◽

2011 ◽

Vol 305 (3-4) ◽

pp. 283-289 ◽

Cited By ~ 41

Author(s):

J. Paul Winberry ◽

Sridhar Anandakrishnan ◽

Douglas A. Wiens ◽

Richard B. Alley ◽

Knut Christianson

Keyword(s):

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Slip Motion

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Basal mechanics of ice streams: Insights from the stick-slip motion of Whillans Ice Stream, West Antarctica

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jf001035 ◽

2009 ◽

Vol 114 (F1) ◽

Cited By ~ 63

Author(s):

J. Paul Winberry ◽

Sridhar Anandakrishnan ◽

Richard B. Alley ◽

Robert A. Bindschadler ◽

Matt A. King

Keyword(s):

West Antarctica ◽

Ice Streams ◽

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Slip Motion

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Tidal pacing, skipped slips and the slowdown of Whillans Ice Stream, Antarctica

Journal of Glaciology ◽

10.3189/2014jog14j038 ◽

2014 ◽

Vol 60 (222) ◽

pp. 795-807 ◽

Cited By ~ 38

Author(s):

J. Paul Winberry ◽

Sridhar Anandakrishnan ◽

Richard B. Alley ◽

Douglas A. Wiens ◽

Martin J. Pratt

Keyword(s):

Elastic Strain ◽

Temporal Evolution ◽

Flow Speed ◽

Stick Slip ◽

Ice Stream ◽

Steady Rate ◽

Decadal Scale ◽

Whillans Ice Stream ◽

Stick Slip Motion

AbstractWe summarize new observations of the deceleration and stick–slip motion of Whillans Ice Stream (WIS), Antarctica. We refine the location of the large sticky spots that resist motion between slip events, the locations of which are controlled by the patterns of subglacial water flow. Our examination of the long-term velocity time series for the ice stream reveals that the decadal-scale deceleration is not occurring at a steady rate, but varies at the sub-decadal timescale. This unsteady deceleration modulates the temporal evolution of a broad (~50 km across) surface-elevation bulge forming at the junction between the relatively narrow upstream portion of the ice stream and broad ice plain that constitutes the downstream end of WIS. Comparison of observations from April 2003 and November 2010 reveals significant changes in the tidally modulated stick–slip cycle that regulates motion on the ice plain. We observe that the timing of slip events has become less regular in response to decreased flow speed in the upstream portions of the ice stream. The decreased regularity of slip events has reduced the release of stored elastic strain during slip events, increasing the rate of deceleration.

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Dynamics of Stick-Slip Motion, Whillans Ice Stream, Antarctica

Quaternary International ◽

10.1016/j.quaint.2012.08.1876 ◽

2012 ◽

Vol 279-280 ◽

pp. 536

Author(s):

J. Paul Winberry

Keyword(s):

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Slip Motion

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Stick–slip behavior of ice streams: modeling investigations

Annals of Glaciology ◽

10.3189/172756409789624274 ◽

2009 ◽

Vol 50 (52) ◽

pp. 87-94 ◽

Cited By ~ 42

Author(s):

Olga V. Sergienko ◽

Douglas R. MacAyeal ◽

Robert A. Bindschadler

Keyword(s):

West Antarctica ◽

Ice Streams ◽

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Spatial Propagation ◽

The Difference ◽

Stick Slip Motion ◽

Transitional Phase ◽

Slip Motion

AbstractA puzzling phenomenon of ice-stream flow is the stick–slip motion displayed by Whillans Ice Stream (WIS), West Antarctica. In this study we test the hypothesis that the WIS stick–slip motion has features similar to those of other known stick–slip systems, and thus might be of the same origin. To do so, we adapt a simple mechanical model widely used in seismology to study classic stick–slip behavior observed in tectonic faults, in which the difference between static and dynamic friction allows for the generation and spatial propagation of abrupt slip events. We show how spatial variability in friction properties, as well as a periodic forcing intended to mimic the effect of tides, can reproduce the observed duration and periodicity of stick–slip motion in an ice stream. An intriguing aspect of the association of WIS with mechanical stick–slip oscillators is that the onset of stick–slip cycling from a condition of permanent slip appears to be associated with the reduction in overall speed of WIS. If this association is true, then stick–slip behavior of WIS is a transitional phase of behavior associated with the ice stream's recent deceleration.

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Tidally driven stick–slip motion in the mouth of Whillans Ice Stream, Antarctica

Annals of Glaciology ◽

10.3189/172756403781816284 ◽

2003 ◽

Vol 36 ◽

pp. 263-272 ◽

Cited By ~ 49

Author(s):

Robert A. Bindschadler ◽

Patricia L. Vornberger ◽

Matt A. King ◽

Laurie Padman

Keyword(s):

High Tide ◽

Spring Tide ◽

Shear Stresses ◽

Motion Events ◽

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Tide Period ◽

Slip Motion

AbstractWe show that the ice plain in the mouth of Whillans Ice Stream (formerly Ice Stream B), Antarctica, moves by stick–slip motion. During a spring-tide period, rapid motions regularly occur near high tide and during falling tide. This correlation is weaker during a neap-tide period when the tidal magnitudes are less. Precise timing of these motion events suggests that they propagate through the region with a mean velocity of 88 m s−1.We hypothesize that this speed is associated with the propagation of shear waves through a wet subglacial till. Motion events are also seen on more smoothly flowing floating ice. Event delays are very short between grounded and floating stations, suggesting the events propagate through the ice shelf as an elastic wave. We further hypothesize the events are caused by the interaction of a sticky bed, the accumulation of stored elastic strain through the compression of ice by upstream inflow, and tidal forcing. Motion events seem to be triggered either by reduction of vertical normal stresses at high tide or by the increase of shear stresses from sub-shelf ocean currents during falling tide. Event magnitudes are not related to the length of the preceding quiescent period, suggesting significant viscous dissipation within the till.

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A model of processive walking and slipping of kinesin-8 molecular motors

Scientific Reports ◽

10.1038/s41598-021-87532-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ping Xie

Keyword(s):

Single Molecule ◽

Molecular Motors ◽

External Load ◽

Molecular Motor ◽

Velocity Versus ◽

Stick Slip ◽

Load Dependence ◽

Chemomechanical Coupling ◽

Similarities And Differences ◽

Stick Slip Motion

AbstractKinesin-8 molecular motor can move with superprocessivity on microtubules towards the plus end by hydrolyzing ATP molecules, depolymerizing microtubules. The available single molecule data for yeast kinesin-8 (Kip3) motor showed that its superprocessive movement is frequently interrupted by brief stick–slip motion. Here, a model is presented for the chemomechanical coupling of the kinesin-8 motor. On the basis of the model, the dynamics of Kip3 motor is studied analytically. The analytical results reproduce quantitatively the available single molecule data on velocity without including the slip and that with including the slip versus external load at saturating ATP as well as slipping velocity versus external load at saturating ADP and no ATP. Predicted results on load dependence of stepping ratio at saturating ATP and load dependence of velocity at non-saturating ATP are provided. Similarities and differences between dynamics of kinesin-8 and that of kinesin-1 are discussed.

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GRANULAR FAILURE: THE ORIGIN OF EARTHQUAKES?

International Journal of Modern Physics B ◽

10.1142/s0217979209063699 ◽

2009 ◽

Vol 23 (28n29) ◽

pp. 5374-5382 ◽

Cited By ~ 4

Author(s):

MASSIMO PICA CIAMARRA ◽

LUCILLA DE ARCANGELIS ◽

EUGENIO LIPPIELLO ◽

CATALDO GODANO

Keyword(s):

Confining Pressure ◽

Stick Slip ◽

Slip Regime ◽

Constant Rate ◽

Large Fluctuations ◽

System Flow ◽

System Phase Diagram ◽

Dynamics Simulations ◽

Stick Slip Motion ◽

System Phase

Via Molecular Dynamics simulations, we investigate the stick-slip motion in a model of fault, where two surfaces subject to a constant confining pressure P, and enclosing granular particles, are subject a shear stress σ. When the system sticks, the stress increases with a constant rate [Formula: see text], while the stress decreases when the system flow. We dermine the system 'phase diagram' in the pressure P load velocity [Formula: see text] plane, locating the transition form the continuos flow regime to the stick-slip regimes, and show that the transition between these two regimes is characterized by the presence of large fluctuations. In the stick-slip regime, the system reproduces the behaviour of a segment of a fault of fixed lenght.

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