scholarly journals Stick–slip behavior of ice streams: modeling investigations

2009 ◽  
Vol 50 (52) ◽  
pp. 87-94 ◽  
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.

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

2009 ◽  
Vol 114 (F1) ◽  
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

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

2011 ◽  
Vol 305 (3-4) ◽  
pp. 283-289 ◽  
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

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

2003 ◽  
Vol 36 ◽  
pp. 263-272 ◽  
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.

scholarly journals Melting and freezing beneath the Ross ice streams, Antarctica

2004 ◽  
Vol 50 (168) ◽  
pp. 96-108 ◽  
Author(s):  
Ian Joughin ◽  
Slawek Tulaczyk ◽  
Douglas R. MacAyeal ◽  
Hermann Engelhardt
Keyword(s):  
Steady Flow ◽  
Temperature Model ◽  
West Antarctica ◽  
Ice Streams ◽  
Horizontal Advection ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Shear Heating ◽  
Strain Heating ◽  
Inland Ice

AbstractWe have estimated temperature gradients and melt rates at the bottom of the ice streams in West Antarctica. Measured velocities were used to include the effects of horizontal advection and strain heating in the temperature model and to determine shear heating at the bed. Our modeled temperatures agree well with measured temperatures from boreholes in regions of steady flow. We find that ice-stream tributaries and the inland ice account for about 87% of the total melt generated beneath the Ross ice streams and their catchments. Our estimates indicate that the ice plains of Whillans Ice Stream and Ice Stream C (even when active) have large areas subject to basal freezing, confirming earlier estimates that import of water from upstream is necessary to sustain motion. The relatively low melt rates on Whillans Ice Stream are consistent with observations of deceleration over the last few decades and suggest a shutdown may take place in the future, possibly within this century. While there are pockets of basal freezing beneath Ice Streams D and E, there are larger areas of basal melt that produce enough melt to more than offset the freezing, which is consistent with inferences of relatively steady flow for these ice streams over the last millennium.

scholarly journals Micro-earthquakes beneath Ice Streams Β and C, West Antarctica: observations and implications

1993 ◽  
Vol 39 (133) ◽  
pp. 455-462 ◽  
Author(s):  
S. Anandakrishnan ◽  
C. R. Bentley
Keyword(s):  
Fault Plane ◽  
Source Parameters ◽  
West Antarctica ◽  
Ice Streams ◽  
Rapid Movement ◽  
Plane Analysis ◽  
Ice Stream ◽  
The Difference ◽  
Ice Stream B ◽  
Active Flow

Abstract Micro-earthquakes have been monitored at two locations on Ice Stream Β and one on Ice Stream C using a seismographic array built specifically for that purpose. Subglacial micro-earthquakes arc 20 times more abundant beneath Ice Stream C than beneath Ice Stream B, despite the 100 times more rapid movement of Ice Stream B. Triangulation shows the foci beneath Ice Stream C, like those beneath Ice Stream B, to be within a few meters of the base of the ice, presumably within the uppermost part of the bed, and fault-plane analysis indicates slips on horizontal planes at about a 30° angle to the presumed direction of formerly active flow. Source parameters, computed from spectra of the arrivals, confirmed that the speed of slip is three orders of magnitude faster beneath Ice Stream C than beneath Ice Stream Β which means that a five orders-of-magnitude greater fraction of the velocity of Ice Stream C is contributed by the faulting, although that fraction is still small. We attribute the difference in activity beneath the two ice streams to the loss of dilatancy in the till beneath Ice Stream C in the process that led to its stagnation.

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

2014 ◽  
Vol 60 (222) ◽  
pp. 795-807 ◽  
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.

Simultaneous teleseismic and geodetic observations of the stick–slip motion of an Antarctic ice stream

Nature ◽  
2008 ◽  
Vol 453 (7196) ◽  
pp. 770-774 ◽  
Author(s):  
Douglas A. Wiens ◽  
Sridhar Anandakrishnan ◽  
J. Paul Winberry ◽  
Matt A. King
Keyword(s):  
Stick Slip ◽  
Ice Stream ◽  
Stick Slip Motion ◽  
Slip Motion

scholarly journals Basal melt rates beneath Whillans Ice Stream, West Antarctica

2010 ◽  
Vol 56 (198) ◽  
pp. 647-654 ◽  
Author(s):  
Lucas H. Beem ◽  
Ken C. Jezek ◽  
C.J. Van Der Veen
Keyword(s):  
West Antarctica ◽  
Ice Streams ◽  
Stress Regime ◽  
Basal Resistance ◽  
West Antarctic ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Fast Flow ◽  
Insight Into ◽  
Streaming Flow

AbstractBasal water lubricates and enables the fast flow of the West Antarctic ice streams which exist under low gravitational driving stress. Identification of sources and rates of basal meltwater production can provide insight into the dynamics of ice streams and the subglacial hydrology, which remain insufficiently described by glaciological theory. Combining measurements and analytic modeling, we identify two regions where basal meltwater is produced beneath Whillans Ice Stream, West Antarctica. Downstream of the onset of shear crevasses, strong basal melt (20–50 mm a−1) is concentrated beneath the relatively narrow shear margins. Farther upstream, melt rates are consistently 3–7 mm a−1 across the width of the ice stream. We show that the transition in melt-rate patterns is coincident with the onset of shear margin crevassing and streaming flow and related to the development of significant lateral shear resistance, which reorganizes the resistive stress regime and induces a concentration of basal resistance adjacent to the shear margin. Finally, we discuss how downstream freeze-on in the ice-stream center coupled with melt beneath the shear margin might result in a slowing but widening ice stream.

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

2016 ◽  
Vol 4 ◽  
Author(s):  
Ryan T. Walker ◽  
Byron R. Parizek ◽  
Richard B. Alley ◽  
Sophie M. J. Nowicki
Keyword(s):  
Stream Flow ◽  
Viscoelastic Model ◽  
Stick Slip ◽  
Ice Stream ◽  
Stick Slip Motion ◽  
Slip Motion
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