Onset of Streaming Flow in the Siple Coast Region, West Antarctica

2013 ◽  
pp. 123-136 ◽  
Author(s):  
Robert Bindschadler ◽  
Jonathan Bamber ◽  
Sridhar Anandakrishnan
Keyword(s):  
West Antarctica ◽  
Coast Region ◽  
Streaming Flow

scholarly journals The onset area of Ice Stream D, West Antarctica

2000 ◽  
Vol 46 (152) ◽  
pp. 95-101 ◽  
Author(s):  
Robert Bindschadler ◽  
Xin Chen ◽  
Patricia Vornberger
Keyword(s):  
Strain Rate ◽  
Global Positioning System ◽  
Landsat Imagery ◽  
Surface Flow ◽  
West Antarctica ◽  
The Past ◽  
Ice Stream ◽  
Global Positioning ◽  
Longitudinal Strain Rate ◽  
Streaming Flow

AbstractSurface flow in a 10 000 km2 expanse of the onset area of Ice Stream D, West Antarctica, was measured by repeat, precise global positioning system surveys over a 1 year interval. The pattern of velocity and strain rate shows the development of Ice Stream D, the major flow into which originates south of Byrd station and follows the course of a deep bed channel. Plotting of the driving stress vs the ratio of velocity and ice thickness identifies the onset of streaming flow (roughly 140 km downstream of Byrd station) as a transition between deformation flow and sliding flow. Along the kinematic center line of the developing ice stream, the ice rheology is linear at stresses below 0.6 bar, and appears temperate at the base well before the onset of streaming is reached. The onset corresponds to a maximum driving stress of 0.8 bar. It occurs downstream of a slight increase in longitudinal strain rate where stronger along-flow lineations are apparent in Landsat imagery, and after the ice has passed the center of an overdeepening in the bed channel. No current deviation from equilibrium is detected in this region, but a set of flow stripes misaligned with present flow indicates significant changes in flow have occurred in the past.

scholarly journals Crevasse patterns at the onset to Ice Stream B, West Antarctica

2001 ◽  
Vol 47 (156) ◽  
pp. 29-36 ◽  
Author(s):  
S. F. Price ◽  
I. M. Whillans
Keyword(s):  
Satellite Imagery ◽  
Water Production ◽  
West Antarctica ◽  
Ice Stream ◽  
Water Production Rate ◽  
Ice Stream B ◽  
And Storage ◽  
Possible Cause ◽  
Over Time ◽  
Streaming Flow

AbstractSequential satellite imagery and modeling are used to investigate crevasse patterns at the head of Ice Stream B tributary B1b. The crevasses, informally called the “chromosomes”, form at the upstream limit to B1b’s northern shear margin and chaotic crevasse zone. We find that the onset to crevasse formation, and by inference the onset to streaming flow, has migrated upstream over time at a mean rate of 230(16) m a−1. A possible cause for that migration is changes in net basal friction due to changes in basal water production rate and storage.

scholarly journals Ice-core insights into the flow and shut-down of Ice Stream C, West Antarctica

2003 ◽  
Vol 37 ◽  
pp. 123-128 ◽  
Author(s):  
Donald E. Voigt ◽  
Richard B. Alley ◽  
Sridhar Anandakrishnan ◽  
Matthew K. Spencer
Keyword(s):  
Power Law ◽  
Creep Behavior ◽  
Stream Flow ◽  
Ice Core ◽  
High Density ◽  
West Antarctica ◽  
Ice Stream ◽  
Central Regions ◽  
Power Law Creep ◽  
Streaming Flow

AbstractVigorous flow of central regions of Ice Stream C, West Antarctica, near the UpC camp ended about the year 1830, based on analysis of a firn and ice core taken at the camp. Ice-stream flow was characterized by repeated fracturing and healing, probably subsurface, especially near the onset of streaming flow. High longitudinal stresses caused fracturing, recrystallization of the ice and elongation of bubbles, and enhanced densification rates of high-density firn indicating power-law-creep behavior.

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 New and improved determinations of velocity of Ice Streams B and C, West Antarctica

1993 ◽  
Vol 39 (133) ◽  
pp. 483-590 ◽  
Author(s):  
I. M. Whillans ◽  
C.J. Van Der Veen
Keyword(s):  
Stream Flow ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Flow ◽  
Ice Stream ◽  
Fast Ice ◽  
Ice Stream B ◽  
Shelf Flow ◽  
Streaming Flow

AbstractMeasurements of velocity have been made on and next to Ice Streams Β and C, West Antarctica. The results are more precise than previous work and constitute a 93% increase in the number of values. These velocities are used to describe the confluence of flow into the ice streams and the development of fast ice-stream flow. The onset of fast-streaming flow occurs in many separate tributaries that coalesce down-glacier into the major ice streams. For those inter-stream ridges that have been studied, the flow is consistent with steady state. Along Ice Stream B, gradients in longitudinal stress offer little resistance to the ice flow. The transition from basal-drag control to ice-shelf flow is achieved through reduced drag at the glacier base and increased resistance associated with lateral drag. Velocities in the trunk of Ice Stream C are nearly zero but those at the up-glacial head are similar to those at the head of Ice Stream B.

scholarly journals New and improved determinations of velocity of Ice Streams B and C, West Antarctica

1993 ◽  
Vol 39 (133) ◽  
pp. 483-590 ◽  
Author(s):  
I. M. Whillans ◽  
C.J. Van Der Veen
Keyword(s):  
Stream Flow ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Streams ◽  
Ice Flow ◽  
Ice Stream ◽  
Fast Ice ◽  
Ice Stream B ◽  
Shelf Flow ◽  
Streaming Flow

Abstract Measurements of velocity have been made on and next to Ice Streams Β and C, West Antarctica. The results are more precise than previous work and constitute a 93% increase in the number of values. These velocities are used to describe the confluence of flow into the ice streams and the development of fast ice-stream flow. The onset of fast-streaming flow occurs in many separate tributaries that coalesce down-glacier into the major ice streams. For those inter-stream ridges that have been studied, the flow is consistent with steady state. Along Ice Stream B, gradients in longitudinal stress offer little resistance to the ice flow. The transition from basal-drag control to ice-shelf flow is achieved through reduced drag at the glacier base and increased resistance associated with lateral drag. Velocities in the trunk of Ice Stream C are nearly zero but those at the up-glacial head are similar to those at the head of Ice Stream B.

scholarly journals Force balance along an inland tributary and onset to Ice Stream D, West Antarctica

2002 ◽  
Vol 48 (160) ◽  
pp. 20-30 ◽  
Author(s):  
Stephen F. Price ◽  
Robert A. Bindschadler ◽  
Christina L. Hulbe ◽  
Donald D. Blankenship
Keyword(s):  
Flow Behavior ◽  
Local Stress ◽  
Force Balance ◽  
Physical Interaction ◽  
West Antarctica ◽  
Stress Concentrations ◽  
Ice Flow ◽  
Stress Gradients ◽  
Ice Stream ◽  
Streaming Flow

AbstractThe transition from inland- to streaming-style ice flow near to and upstream from the onset to Ice Stream D, West Antarctica, is investigated using the force-balance technique. Basal drag provides the majority of the flow resistance over the study area but is substantially modified by non-local stress gradients. Lateral drag increases with distance downstream, balancing ∼50–100% of the driving stress at the onset. Longitudinal stress gradients (LSG) are also found to be significant, an observation that distinguishes ice flow in this region from the inland- and streaming-flow regimes that bound it, in which LSG are usually negligible. LSG decrease the spatial variability in basal drag and sliding speed and increase the area of the bed over which frictional melting occurs. Overall, LSG decrease the resistive influence of basal stress concentrations and increase the spatial uniformity of basal sliding. These observations suggest that streaming flow develops as an integrated response to the physical interaction between the ice and its bed over an extended region upstream from the onset, rather than being solely due to changes in basal characteristics at the onset. An implication is that non-steady-flow behavior upstream from the onset may ultimately propagate downstream and result in non-steady behavior at the onset.

scholarly journals Dilatant till layer near the onset of streaming flow of Ice Stream C, West Antarctica, determined by AVO (amplitude vs offset) analysis

2003 ◽  
Vol 36 ◽  
pp. 283-286 ◽  
Author(s):  
Sridhar Anandakrishnan
Keyword(s):  
Acoustic Impedance ◽  
Stream Flow ◽  
High Water ◽  
Angle Of Incidence ◽  
West Antarctica ◽  
Wave Velocities ◽  
West Antarctic ◽  
Shear Wave Velocities ◽  
Ice Stream ◽  
Streaming Flow

AbstractA powerful seismic technique that exploits the phase of the ice-bottom reflections shows that soft till is widespread beneath a West Antarctic ice stream very close to the onset of streaming flow. The amplitude vs offset (AVO) method measures the change in amplitude of the reflection as a function of increasing angle of incidence. For a decrease in acoustic impedance with depth, the reflection phase is negative at low angles of impedance but positive at intermediate angles. The change in phase by 180° is an obvious and robust measure of the relative acoustic impedance contrasts. This technique is only usable when there is a change in phase vs offset, conditions which obtain for “UpB-type” tills (high water pressures and porosity, low compressional- and shear-wave velocities, similar to those observed at Upstream B camp). I have applied this technique to the far upstream regions of Ice Stream C and find that a dilatant ( and presumably deforming), relatively thick (meters) till layer has formed beneath the ice stream within tens of km of the region identified as the transition from inland flow to ice-stream flow. These results suggest that the onset of rapid basal motion is linked to the formation of this deforming subglacial layer.

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