scholarly journals Surface morphology and internal layer stratigraphy in the downstream end of Kamb Ice Stream, West Antarctica

2005 ◽  
Vol 51 (174) ◽  
pp. 423-431 ◽  
Author(s):  
G. A. Catania ◽  
H. Conway ◽  
C.F. Raymond ◽  
T.A. Scambos
Keyword(s):  
Satellite Images ◽  
Flow Direction ◽  
Internal Layer ◽  
Internal Layers ◽  
West Antarctica ◽  
Ice Flow ◽  
Ice Stream ◽  
Grounding Line ◽  
Different Origins ◽  
Kamb Ice Stream

AbstractSatellite images of Kamb Ice Stream (formerly Ice Stream C), West Antarctica, reveal several long, curved linear features (lineations) oriented sub-parallel to the ice-flow direction. We use ground-based radar to characterize the internal layer stratigraphy of these lineations and the terrains that they bound. Some lineations are relict ice-stream shear margins, identified by hyperbolic diffractors near the surface (interpreted to be buried crevasses) and highly disturbed internal layers at depth. Satellite images show another set of lineations outside the relict margins that wrap around the ends of the surrounding inter-ice-stream ridges. Internal layers beneath these lineations are downwarped strongly into a syncline shape. The internal stratigraphy of the terrain between these lineations and the relict margins is characterized by deep hyperbolic line diffractors. Our preferred hypothesis for the origin of this terrain is that it was floating sometime in the past; the deep hyperbolas are interpreted to be basal crevasses, and the strongly downwarped internal layers mark the position of a relict grounding line. Our study shows that lineations and intervening terrains have different internal layer characteristics implying different origins. Differentiation between these features is not possible using satellite images alone.

scholarly journals Persistent tracers of historic ice flow in glacial stratigraphy near Kamb Ice Stream, West Antarctica

2018 ◽  
Vol 12 (9) ◽  
pp. 2821-2829 ◽  
Author(s):  
Nicholas Holschuh ◽  
Knut Christianson ◽  
Howard Conway ◽  
Robert W. Jacobel ◽  
Brian C. Welch
Keyword(s):  
Large Scale ◽  
Ross Sea ◽  
Accumulation Rate ◽  
Volcanic Complex ◽  
West Antarctica ◽  
Ice Flow ◽  
Ice Stream ◽  
Grounding Line ◽  
Flow Pathways ◽  
Kamb Ice Stream

Abstract. Variations in properties controlling ice flow (e.g., topography, accumulation rate, basal friction) are recorded by structures in glacial stratigraphy. When anomalies that disturb the stratigraphy are fixed in space, the structures they produce advect away from the source and can be used to trace flow pathways and reconstruct ice-flow patterns of the past. Here we provide an example of one of these persistent tracers: a prominent unconformity in the glacial layering that originates at Mt. Resnik, part of a subglacial volcanic complex near Kamb Ice Stream in central West Antarctica. The unconformity records a change in the regional thinning behavior seemingly coincident (∼3440±117 a) with stabilization of grounding-line retreat in the Ross Sea Embayment. We argue that this feature records both the flow and thinning history far upstream of the Ross Sea grounding line, indicating a limited influence of observed ice-stream stagnation cycles on large-scale ice-sheet routing over the last ∼ 5700 years.

scholarly journals Persistent Tracers of Historic Ice Flow in Glacial Stratigraphy near Kamb Ice Stream, West Antarctica

2018 ◽  
Author(s):  
Nicholas Holschuh ◽  
Knut Christianson ◽  
Howard Conway ◽  
Robert W. Jacobel ◽  
Brian C. Welch
Keyword(s):  
Large Scale ◽  
Ross Sea ◽  
Accumulation Rate ◽  
Volcanic Complex ◽  
West Antarctica ◽  
Ice Flow ◽  
Ice Stream ◽  
Grounding Line ◽  
Flow Pathways ◽  
Kamb Ice Stream

Abstract. Variations in properties controlling ice flow (e.g., topography, accumulation rate, basal friction) are recorded by structures in glacial stratigraphy. When anomalies that disturb the stratigraphy are fixed in space, the structures they produce advect away from the source, and can be used to trace flow pathways and reconstruct ice-flow patterns of the past. Here we provide an example of one of these persistent tracers: a prominent unconformity in the glacial layering that originates at Mt. Resnik, part of a subglacial volcanic complex near Kamb Ice Stream in central West Antarctica. The unconformity records a change in the regional thinning behavior seemingly coincident (∼ 3440 ± 117a) with stabilization of grounding-line retreat along the Ross Ice Shelf. We argue that this feature records both the flow and thinning history far upstream of the Ross Sea grounding line, indicating a limited influence of observed ice-stream stagnation cycles on large-scale ice-sheet routing over the last ∼ 5700 years.

scholarly journals Deformation in Rutford Ice Stream, West Antarctica: measuring shear-wave anisotropy from icequakes

2013 ◽  
Vol 54 (64) ◽  
pp. 105-114 ◽  
Author(s):  
S.R. Harland ◽  
J.-M. Kendall ◽  
G.W. Stuart ◽  
G.E. Lloyd ◽  
A.F. Baird ◽  
...  
Keyword(s):  
Shear Wave ◽  
Flow Direction ◽  
Transversely Isotropic ◽  
Shear Wave Splitting ◽  
Ice Crystal ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Ice Stream ◽  
Wave Splitting

Abstract Ice streams provide major drainage pathways for the Antarctic ice sheet. The stress distribution and style of flow in such ice streams produce elastic and rheological anisotropy, which informs ice-flow modelling as to how ice masses respond to external changes such as global warming. Here we analyse elastic anisotropy in Rutford Ice Stream, West Antarctica, using observations of shear-wave splitting from three-component icequake seismograms to characterize ice deformation via crystal-preferred orientation. Over 110 high-quality measurements are made on 41 events recorded at five stations deployed temporarily near the ice-stream grounding line. To the best of our knowledge, this is the first well-documented observation of shear-wave splitting from Antarctic icequakes. The magnitude of the splitting ranges from 2 to 80 ms and suggests a maximum of 6% shear-wave splitting. The fast shear-wave polarization direction is roughly perpendicular to ice-flow direction. We consider three mechanisms for ice anisotropy: a cluster model (vertical transversely isotropic (VTI) model); a girdle model (horizontal transversely isotropic (HTI) model); and crack-induced anisotropy (HTI model). Based on the data, we can rule out a VTI mechanism as the sole cause of anisotropy – an HTI component is needed, which may be due to ice crystal a-axis alignment in the direction of flow or the alignment of cracks or ice films in the plane perpendicular to the flow direction. The results suggest a combination of mechanisms may be at play, which represent vertical variations in the symmetry of ice crystal anisotropy in an ice stream, as predicted by ice fabric models.

scholarly journals Migration of the Siple Dome ice divide, West Antarctica

1998 ◽  
Vol 44 (148) ◽  
pp. 643-652 ◽  
Author(s):  
N. A. Nereson ◽  
C. F. Raymond ◽  
E. D. Waddington ◽  
R. W. Jacobel
Keyword(s):  
Migration Rate ◽  
Internal Layer ◽  
Internal Layers ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Flow Models ◽  
The Past ◽  
Siple Dome ◽  
Local Accumulation

AbstractThe non-linearity of the ice-flow law or a local accumulation low over an ice divide can cause isochrones (internal layers) to be shallower under the divide relative to the flanks, forming a “divide bump” in the internal layer pattern. This divide signature is analyzed using ice-flow models and inverse techniques to detect and quantify motion of the Siple Dome ice divide, West Antarctica. The principal feature indicating that migration has occurred is a distinct tilt of the axis of the peaks of the warped internal layers beneath the divide. The calculated migration rate is 0.05-0.50 m a−1 toward Ice Stream D and depends slightly on whether the divide bump is caused by the non-linearity of ice flow or by a local accumulation low. Our calculations also suggest a strong south-north accumulation gradient of 5-10 x 10−6 a−1 in a narrow zone north of the divide. A consequence of divide migration is that pre-Holocene ice is thickest about 0.5 km south of the present divide position. Divide motion indicates that non-steady processes, possibly associated with activity of the bounding ice streams, are affecting the geometry of Siple Dome. The migration rate is sufficiently slow that the divide bump is maintained in the internal layer pattern at all observable depths. This suggests that major asynchronous changes in the elevation or position of the bounding ice streams are unlikely over at least the past 103-104 years.

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 Interpretation of radar-detected internal layer folding in West Antarctic ice streams

1993 ◽  
Vol 39 (133) ◽  
pp. 528-537 ◽  
Author(s):  
W. Jacobel Robert ◽  
M. Gades Anthony ◽  
L. Gottschling David ◽  
M. Hodge Steven ◽  
L. Wright David
Keyword(s):  
Flow Direction ◽  
Low Frequency ◽  
Internal Layers ◽  
West Antarctica ◽  
Ice Streams ◽  
West Antarctic ◽  
Ice Stream ◽  
High Resolution Images ◽  
Basal Shear ◽  
Inland Ice

AbstractLow-frequency surface-based radar-profiling experiments on Ice Streams Β and C, West Antarctica, have yielded high-resolution images which depict folding of the internal layers that can aid in the interpretation of ice-stream dynamics. Unlike folding seen in most earlier radar studies of ice sheets, the present structures have no relationship to bedrock topography and show tilting of their axial fold planes in the flow direction. Rather than being standing waves created by topography or local variations in basal shear stress, the data show that these folds originate upstream of the region of streaming flow and are advected into the ice streams. The mechanism for producing folds is hypothesized to be changes in the basal boundary conditions as the ice makes the transition from inland ice to ice-stream flow. Migration of this transition zone headward can then cause folds in the internal layering to be propagated down the ice streams.

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 Kamb Ice Stream flow history and surge potential

2013 ◽  
Vol 54 (63) ◽  
pp. 287-298 ◽  
Author(s):  
Hermann Engelhardt ◽  
Barclay Kamb
Keyword(s):  
Video Camera ◽  
Hot Water ◽  
West Antarctica ◽  
Time Intervals ◽  
Ice Flow ◽  
Ice Stream ◽  
History Of ◽  
Fast Ice ◽  
Fast Motion ◽  
Kamb Ice Stream

AbstractA basal zone, tens of meters thick, of debris-laden ice was observed in Kamb Ice Stream, West Antarctica, using a video camera lowered into boreholes made by hot-water drilling. The debris content varies, sometimes abruptly, forming a sequence of layers that reflect the complex history of fast ice flow and bed interaction. In most parts, the concentration of debris is low, a few percent by weight, with particles, often mud clots, dispersed in a matrix of clear ice. The nature of the debris distribution can be interpreted in terms of specific time intervals in the history of fast motion of Kamb Ice Stream including processes leading up to the termination of its streaming behavior and possible reactivation.

scholarly journals Anisotropic ice flow leading to the onset of Ice Stream D, West Antarctica: numerical modelling based on the observations from Byrd Station borehole

2003 ◽  
Vol 37 ◽  
pp. 397-403 ◽  
Author(s):  
Weili Wang ◽  
H. Jay Zwally ◽  
Christina L. Hulbe ◽  
Martin J. Siegert ◽  
Ias Joughin
Keyword(s):  
Crystal Orientation ◽  
Internal Layers ◽  
Fabric Anisotropy ◽  
West Antarctica ◽  
Ice Flow ◽  
Ice Stream ◽  
Radio Echo Sounding ◽  
The Last Glacial Maximum ◽  
Particle Paths ◽  
The Last Glacial

AbstractAn ice-sheet flowline model is used to simulate the flow of ice along two particle paths toward the onset to Ice Stream D, West Antarctica. One path is near the centre line of the main tributary to the ice stream, while the second passes by the Byrd Station borehole site. In this paper, we analyze the flow of the moderately fast-flowing tributaries in terms of ice-fabric anisotropy and estimate the steady-state ice-flow regions with the compatible developed crystal orientation fabrics along two particle paths. Comparison between modelled isochrones and internal layers detected from radio-echo sounding surveys in the area is used to suggest that flow upstream of the onset to Ice Stream D appears to have been stable since at least the Last Glacial Maximum.

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