scholarly journals Mid‐Holocene Grounding Line Retreat and Readvance at Whillans Ice Stream, West Antarctica

2020 ◽  
Vol 47 (15) ◽  
Author(s):  
R. A. Venturelli ◽  
M. R. Siegfried ◽  
K. A. Roush ◽  
W. Li ◽  
J. Burnett ◽  
...  
Keyword(s):  
West Antarctica ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Grounding Line

scholarly journals Changes in the ice plain of Whillans Ice Stream, West Antarctica

2005 ◽  
Vol 51 (175) ◽  
pp. 620-636 ◽  
Author(s):  
Robert Bindschadler ◽  
Patricia Vornberger ◽  
Laurence Gray
Keyword(s):  
West Antarctica ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Grounding Line ◽  
Local Areas ◽  
The Mean ◽  
Geometric Changes ◽  
Thinning Rate

AbstractData from the mouth of the decelerating Whillans Ice Stream (WIS), West Antarctica, spanning 42 years are reviewed. Deceleration has continued, with local areas of both thinning and thickening occurring. The mean thinning rate is 0.48 ± 0.77 ma–1. No consistent overall pattern is observed. Ice thickens immediately upstream of Crary Ice Rise where deceleration and divergence are strongest, suggesting expanded upstream influence of the ice rise. Thinning is prevalent on the Ross Ice Shelf. Grounding-line advance at a rate of 0.3 km a–1 is detected in a few locations. Basal stresses vary across an ice-stream transect with a zone of enhanced flow at the margin. Marginal shear is felt at the ice-stream center. Mass-balance values are less negative, but larger errors of earlier measurements mask any possible temporal pattern. Comparisons of the recent flow field with flow stripes suggest WIS contributes less ice to the deep subglacial channel carved by Mercer Ice Stream and now flows straighter. The general lack of geometric changes suggests that the regional velocity decrease is due to changing basal conditions.

scholarly journals Grounding-line dynamics and margin lakes

2014 ◽  
Vol 55 (66) ◽  
pp. 87-96 ◽  
Author(s):  
M.J. Fried ◽  
C.L. Hulbe ◽  
M.A. Fahnestock
Keyword(s):  
Smooth Surfaces ◽  
Line Position ◽  
West Antarctica ◽  
Main Trunk ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Grounding Line ◽  
Different Ages ◽  
History Of ◽  
Regional History

AbstractAt both corners of the now stagnant Kamb Ice Stream (KIS, West Antarctica) outlet, shear margins of different ages confine wedge-shaped areas with relatively flat, smooth surfaces that stagnated before the main trunk of the ice stream. We identify these features as lakes or past lakes, and consider scenarios for their development in a regional history of ongoing adjustment to grounding-line position. We focus here on the centuries leading up to the recent stagnation of KIS, a time when its grounding line appears to have advanced >100km from an earlier upstream location. Starting from stagnation of Crary Ice Rise and changes in the grounding zone of Whillans Ice Stream, we trace feedbacks associated with local thickening, ice grounding and thickness transients that both advance the grounding line and leave remnant lakes in their wake. These lakes in turn promote the development of secondary margins that may appear as ‘margin jumps’ in the ice record.

scholarly journals Sensitivity of Pine Island Glacier, West Antarctica, to changes in ice-shelf and basal conditions: a model study

2002 ◽  
Vol 48 (163) ◽  
pp. 552-558 ◽  
Author(s):  
Marjorie Schmeltz ◽  
Eric Rignot ◽  
Todd K. Dupont ◽  
Douglas R. MacAyeal
Keyword(s):  
Shear Stress ◽  
Element Model ◽  
Shelf Area ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Stream ◽  
Model Study ◽  
Grounding Line ◽  
Glacier Velocity ◽  
Basal Shear

AbstractWe use a finite-element model of coupled ice-stream/ice-shelf flow to study the sensitivity of Pine Island Glacier, West Antarctica, to changes in ice-shelf and basal conditions. By tuning a softening coefficient of the ice along the glacier margins, and a basal friction coefficient controlling the distribution of basal shear stress underneath the ice stream, we are able to match model velocity to that observed with interferometric synthetic aperture radar (InSAR). We use the model to investigate the effect of small perturbations on ice flow. We find that a 5.5–13% reduction in our initial ice-shelf area increases the glacier velocity by 3.5–10% at the grounding line. The removal of the entire ice shelf increases the grounding-line velocity by > 70%. The changes in velocity associated with ice-shelf reduction are felt several tens of km inland. Alternatively, a 5% reduction in basal shear stress increases the glacier velocity by 13% at the grounding line. By contrast, softening of the glacier side margins would have to be increased a lot more to produce a comparable change in ice velocity. Hence, both the ice-shelf buttressing and the basal shear stress contribute significant resistance to the flow of Pine Island Glacier.

scholarly journals Is Ice-Stream Evolution Revealed By Satellite Imagery?

1990 ◽  
Vol 14 ◽  
pp. 273-277 ◽  
Author(s):  
S.N. Stephenson ◽  
R.A. Bindschadler
Keyword(s):  
Stream Flow ◽  
Temporal Evolution ◽  
Thematic Mapper ◽  
Landsat Thematic Mapper ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Ice Shelves ◽  
Ice Stream ◽  
Grounding Line

Ten Landsat Thematic Mapper images together show Ice Streams E, D and most of Ice Stream C on Siple Coast, West Antarctica. The images are interpreted to reveal aspects of both spatial and temporal evolution of the ice streams. Onset of ice-stream flow appears to occur at distributed sites within the ice-stream catchment, and the apparent enhanced flow continues in channels until they join, forming the main ice stream. Most crevassing on these ice streams is associated with features of horizontal dimensions between 5 and 20 km. We suggest these features are caused by bed structures which may be an important source of restraint to ice flow, similar to ice rumples on ice shelves. A pattern of features near the grounding line of the now-stagnant Ice Stream C are interpreted as having formed because there was a period of reduced flux before the ice stream stopped.

scholarly journals Is Ice-Stream Evolution Revealed By Satellite Imagery?

1990 ◽  
Vol 14 ◽  
pp. 273-277 ◽  
Author(s):  
S.N. Stephenson ◽  
R.A. Bindschadler
Keyword(s):  
Stream Flow ◽  
Temporal Evolution ◽  
Thematic Mapper ◽  
Landsat Thematic Mapper ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Ice Shelves ◽  
Ice Stream ◽  
Grounding Line

Ten Landsat Thematic Mapper images together show Ice Streams E, D and most of Ice Stream C on Siple Coast, West Antarctica. The images are interpreted to reveal aspects of both spatial and temporal evolution of the ice streams. Onset of ice-stream flow appears to occur at distributed sites within the ice-stream catchment, and the apparent enhanced flow continues in channels until they join, forming the main ice stream. Most crevassing on these ice streams is associated with features of horizontal dimensions between 5 and 20 km. We suggest these features are caused by bed structures which may be an important source of restraint to ice flow, similar to ice rumples on ice shelves. A pattern of features near the grounding line of the now-stagnant Ice Stream C are interpreted as having formed because there was a period of reduced flux before the ice stream stopped.

scholarly journals The location of the grounding zone of Evans Ice Stream, Antarctica, investigated using SAR interferometry and modelling

2009 ◽  
Vol 50 (52) ◽  
pp. 35-40 ◽  
Author(s):  
Helena J. Sykes ◽  
Tavi Murray ◽  
Adrian Luckman
Keyword(s):  
Stream Flow ◽  
Elastic Beam ◽  
Tidal Height ◽  
Sar Interferometry ◽  
Beam Model ◽  
West Antarctica ◽  
Tidal Model ◽  
Tidal Forcing ◽  
Ice Stream ◽  
Grounding Line

AbstractEvans Ice Stream, West Antarctica, has five tributaries and a complex grounding zone. The grounding zone of Evans Ice Stream, between the landward and seaward limits of tidal flexing, was mapped using SAR interferometry. The width of the mapped grounding zone was compared with that derived from an elastic beam model, and the tidal height changes derived from interferometry were compared with the results of a tidal model. Results show that in 1994 and 1996 the Evans grounding zone was located up to 100 km upstream of its location in the BEDMAP dataset. The grounding line of Evans Ice Stream is subjected to 5 m vertical tidal forcing, which would clearly affect ice-stream flow.

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

scholarly journals Thickness changes on Whillans Ice Stream and Ice Stream C, West Antarctica, derived from laser altimeter measurements

2003 ◽  
Vol 49 (165) ◽  
pp. 223-230 ◽  
Author(s):  
Vandy Blue Spikes ◽  
Beáta M. Csatho ◽  
Gordon S. Hamilton ◽  
Ian M. Whillans
Keyword(s):  
Average Rate ◽  
West Antarctica ◽  
Laser Altimeter ◽  
Equivalent Thickness ◽  
Thickness Change ◽  
Airborne Laser ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Elevation Changes ◽  
Global Sea Level

AbstractRepeat airborne laser altimeter measurements are used to derive surface elevation changes on parts of Whillans Ice Stream and Ice Stream C, West Antarctica. Elevation changes are converted to estimates of ice equivalent thickness change using local accumulation rates, surface snow densities and vertical bedrock motions. The surveyed portions of two major tributaries of Whillans Ice Stream are found to be thinning almost uniformly at an average rate of ∼1 m a−1. Ice Stream C has a complicated elevation-change pattern, but is generally thickening. These results are used to estimate the contribution of each surveyed region to the current rate of global sea-level rise.

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 A deep subglacial embayment adjacent to the grounding line of Institute Ice Stream, West Antarctica

2017 ◽  
Vol 461 (1) ◽  
pp. 161-173 ◽  
Author(s):  
Hafeez Jeofry ◽  
Neil Ross ◽  
Hugh F. J. Corr ◽  
Jilu Li ◽  
Prasad Gogineni ◽  
...  
Keyword(s):  
West Antarctica ◽  
Ice Stream ◽  
Grounding Line
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