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

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.

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Is Ice-Stream Evolution Revealed By Satellite Imagery?

Annals of Glaciology ◽

10.1017/s0260305500008740 ◽

1990 ◽

Vol 14 ◽

pp. 273-277 ◽

Cited By ~ 28

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.

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The use of tiltmeters to study the dynamics of Antarctic ice-shelf grounding lines

Journal of Glaciology ◽

10.1017/s0022143000042799 ◽

1991 ◽

Vol 37 (125) ◽

pp. 51-58 ◽

Cited By ~ 52

Author(s):

A. M. Smith

Keyword(s):

Elastic Beam ◽

Ice Thickness ◽

Elastic Model ◽

Beam Model ◽

Line Position ◽

Stream Data ◽

Ice Shelf ◽

Ice Stream ◽

Grounding Line ◽

Data Coverage

Abstract New tiltmeter data are presented from Doake Ice Rumples on Ronne Ice Shelf, Antarctica. Five sites which showed a tidal ice-shelf flexure have been analysed using an elastic beam model to investigate the variation of flexure amplitude with distance from the grounding line. An earlier study on Rutford Ice Stream which also used an elastic model required an ice thickness much less than that observed. Reworking the Rutford Ice Stream data suggests that this greatly reduced ice thickness is not required, given the current sparse data coverage. The elastic model is used to improve the estimated grounding-line position on Rutford Ice Stream. Some of the difficulties in modelling ice-shelf flexure and locating grounding lines are discussed.

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The use of tiltmeters to study the dynamics of Antarctic ice-shelf grounding lines

Journal of Glaciology ◽

10.3189/s0022143000042799 ◽

1991 ◽

Vol 37 (125) ◽

pp. 51-58 ◽

Cited By ~ 3

Author(s):

A. M. Smith

Keyword(s):

Elastic Beam ◽

Ice Thickness ◽

Elastic Model ◽

Beam Model ◽

Line Position ◽

Stream Data ◽

Ice Shelf ◽

Ice Stream ◽

Grounding Line ◽

Data Coverage

Abstract New tiltmeter data are presented from Doake Ice Rumples on Ronne Ice Shelf, Antarctica. Five sites which showed a tidal ice-shelf flexure have been analysed using an elastic beam model to investigate the variation of flexure amplitude with distance from the grounding line. An earlier study on Rutford Ice Stream which also used an elastic model required an ice thickness much less than that observed. Reworking the Rutford Ice Stream data suggests that this greatly reduced ice thickness is not required, given the current sparse data coverage. The elastic model is used to improve the estimated grounding-line position on Rutford Ice Stream. Some of the difficulties in modelling ice-shelf flexure and locating grounding lines are discussed.

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Persistence and variability of ice-stream grounding lines on retrograde bed slopes

The Cryosphere ◽

10.5194/tc-10-1883-2016 ◽

2016 ◽

Vol 10 (4) ◽

pp. 1883-1896 ◽

Cited By ~ 12

Author(s):

Alexander A. Robel ◽

Christian Schoof ◽

Eli Tziperman

Keyword(s):

Stream Flow ◽

Flow Line ◽

Reverse Direction ◽

West Antarctica ◽

Ice Streams ◽

Basal Resistance ◽

Physical Mechanisms ◽

Ice Stream ◽

Grounding Line ◽

Transient Variations

Abstract. In many ice streams, basal resistance varies in space and time due to the dynamically evolving properties of subglacial till. These variations can cause internally generated oscillations in ice-stream flow. However, the potential for such variations in basal properties is not considered by conventional theories of grounding-line stability on retrograde bed slopes, which assume that bed properties are static in time. Using a flow-line model, we show how internally generated, transient variations in ice-stream state interact with retrograde bed slopes. In contrast to predictions from the theory of the marine ice-sheet instability, our simulated grounding line is able to persist and reverse direction of migration on a retrograde bed when undergoing oscillations in the grounding-line position. In turn, the presence of a retrograde bed may also suppress or reduce the amplitude of internal oscillations in ice-stream state. We explore the physical mechanisms responsible for these behaviors and discuss the implications for observed grounding-line migration in West Antarctica.

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Persistence and Variability of Ice Stream Grounding Lines on Retrograde Bed Slopes

10.5194/tc-2016-18 ◽

2016 ◽

Author(s):

Alexander A. Robel ◽

Christian Schoof ◽

Eli Tziperman

Keyword(s):

Stream Flow ◽

Reverse Direction ◽

Line Position ◽

West Antarctica ◽

Ice Streams ◽

Basal Resistance ◽

Physical Mechanisms ◽

Ice Stream ◽

Grounding Line ◽

Transient Variations

Abstract. In many ice streams, basal resistance varies in space and time due to the dynamically-evolving properties of subglacial till. These variations can cause internally-generated oscillations in ice stream flow. However, the potential for such variations in basal properties are not considered by conventional theories of grounding line stability on retrograde bed slopes, which assume that bed properties are static in time. Using a numerical flowline model, we show how internally-generated, transient variations in ice stream state interact with retrograde bed slopes. In contrast to predictions from the theory of the marine ice sheet instability, our simulated grounding line is able to persist and reverse direction of migration on a retrograde bed when undergoing oscillations in the grounding line position. In turn, the presence of a retrograde bed may also suppress or reduce the amplitude of internal oscillations in ice stream state. We explore the physical mechanisms responsible for these behaviors and discuss the implications for observed grounding line migration in West Antarctica.

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

Journal of Glaciology ◽

10.3189/172756502781831061 ◽

2002 ◽

Vol 48 (163) ◽

pp. 552-558 ◽

Cited By ~ 47

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.

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