Basal conditions at the grounding zone of Whillans Ice Stream, West Antarctica, from ice-penetrating radar

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.

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Melting and freezing beneath the Ross ice streams, Antarctica

Journal of Glaciology ◽

10.3189/172756504781830295 ◽

2004 ◽

Vol 50 (168) ◽

pp. 96-108 ◽

Cited By ~ 75

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.

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Continued deceleration of Whillans Ice Stream, West Antarctica

Geophysical Research Letters ◽

10.1029/2005gl024319 ◽

2005 ◽

Vol 32 (22) ◽

pp. n/a-n/a ◽

Cited By ~ 58

Author(s):

I. Joughin ◽

R. A. Bindschadler ◽

M. A. King ◽

D. Voigt ◽

R. B. Alley ◽

...

Keyword(s):

West Antarctica ◽

Ice Stream ◽

Whillans Ice Stream

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Scale independence of till rheology

Journal of Glaciology ◽

10.3189/172756506781828601 ◽

2006 ◽

Vol 52 (178) ◽

pp. 377-380 ◽

Cited By ~ 37

Author(s):

Slawek Tulaczyk

Keyword(s):

Characteristic Length ◽

West Antarctica ◽

Ice Flow ◽

Length Scales ◽

Ice Stream ◽

In Situ Experiments ◽

Whillans Ice Stream ◽

Speed Up

AbstractRepresentation of till rheology in glaciological models of ice motion over deformable sediments has, until now, focused largely on two end-member cases: (1) linear, or mildly non-linear, viscous rheology and (2) (nearly) plastic rheology. Most laboratory and in situ experiments support the latter model. Hindmarsh (1997) and Fowler (2002, 2003) proposed that experimental results represent the behavior of small till samples (characteristic length scales of ~0.1 to ~1 m) but that till behaves viscously over length scales that are relevant to determination of ice-flow rates in glaciers and ice sheets (~1 km or more). Observations of short speed-up events on the ice plain of Whillans Ice Stream, West Antarctica, provide an opportunity to compare the in situ rheology of this till, integrated over ~10–100 km, with the rheology of till from beneath the same ice stream determined on small laboratory samples and in local borehole experiments. This comparison indicates that the rheology of the subglacial till beneath Whillans Ice Stream is independent of scale.

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Sediment deposition at the modern grounding zone of Whillans Ice Stream, West Antarctica

Geophysical Research Letters ◽

10.1002/grl.50712 ◽

2013 ◽

Vol 40 (15) ◽

pp. 3934-3939 ◽

Cited By ~ 25

Author(s):

Huw J. Horgan ◽

Knut Christianson ◽

Robert W. Jacobel ◽

Sridhar Anandakrishnan ◽

Richard B. Alley

Keyword(s):

Sediment Deposition ◽

West Antarctica ◽

Ice Stream ◽

Whillans Ice Stream

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Decadal-scale variations in ice flow along Whillans Ice Stream and its tributaries, West Antarctica

Journal of Glaciology ◽

10.3189/172756505781829610 ◽

2005 ◽

Vol 51 (172) ◽

pp. 147-157 ◽

Cited By ~ 27

Author(s):

Leigh A. Stearns ◽

Kenneth C. Jezek ◽

C.J. Van Der Veen

Keyword(s):

Aerial Photographs ◽

West Antarctica ◽

Ice Flow ◽

Velocity Gradients ◽

Ice Stream ◽

Spatial Changes ◽

Decadal Scale ◽

Whillans Ice Stream ◽

Satellite Radar ◽

Velocity Changes

AbstractWe investigate velocity changes occurring along Whillans Ice Stream (WIS) by comparing velocities derived from repeat aerial photographs acquired in 1985-89 (average date of 1987) to interferometric satellite radar (InSAR) velocities collected in 1997. Three different analysis methods are applied to the velocity data. First, temporal and spatial changes in velocities are correlated to identifiable features (flowlines, shear margins, bed features) visible on the 1997 RADARSAT Antarctic Mapping Project mosaic. Second, we relate velocity gradients to stresses via the flow law and, along with surface topography and ice-thickness data, apply the force-budget technique to determine the relative importance of driving stress, side drag and basal drag over time. Finally, the mass balance of the main part of WIS is determined for 1987 and 1997. Our results are consistent with previous studies that show an overall deceleration resulting in downstream thickening of the ice stream (Whillans and others, 2001; Joughin and others, 2002).

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

Journal of Glaciology ◽

10.3189/172756505781829070 ◽

2005 ◽

Vol 51 (175) ◽

pp. 620-636 ◽

Cited By ~ 17

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.

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Anisotropy and crystalline fabric of Whillans Ice Stream (West Antarctica) inferred from multicomponent seismic data

Journal of Geophysical Research Solid Earth ◽

10.1002/2014jb011591 ◽

2015 ◽

Vol 120 (6) ◽

pp. 4237-4262 ◽

Cited By ~ 20

Author(s):

Stefano Picotti ◽

Alessandro Vuan ◽

José M. Carcione ◽

Huw J. Horgan ◽

Sridhar Anandakrishnan

Keyword(s):

Seismic Data ◽

West Antarctica ◽

Ice Stream ◽

Multicomponent Seismic ◽

Whillans Ice Stream

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Basal melt rates beneath Whillans Ice Stream, West Antarctica

Journal of Glaciology ◽

10.3189/002214310793146241 ◽

2010 ◽

Vol 56 (198) ◽

pp. 647-654 ◽

Cited By ~ 21

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.

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