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

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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Basal mechanics of ice streams: Insights from the stick-slip motion of Whillans Ice Stream, West Antarctica

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jf001035 ◽

2009 ◽

Vol 114 (F1) ◽

Cited By ~ 63

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

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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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Monitoring glacial thickness changes in the Tibetan Plateau derived from ICESat data

Science and Technology Development Journal ◽

10.32508/stdj.v19i2.677 ◽

2016 ◽

Vol 19 (2) ◽

pp. 130-137

Author(s):

Vu Hien Phan ◽

Roderik Lindenbergh ◽

Massimo Menenti

Keyword(s):

Tibetan Plateau ◽

Average Rate ◽

Weather Conditions ◽

Mountain Range ◽

The Tibetan Plateau ◽

Thickness Change ◽

Shuttle Radar Topographic Mission ◽

Elevation Changes ◽

Water Mass Balance ◽

The Impact

Monitoring glacier changes is essential for estimating the water mass balance of the Tibetan Plateau. Recent research indicates that glaciers at individual regions on the Tibetan Plateau and surroundings are shrinking and thinning during the last decades. Studies considering large regions often ignored however the impact of locally varying weather conditions and terrain characteristics on glacial evolution, i.e. the impact of orographic precipitation and variation in solar radiation. Our hypothesis is therefore that adjacent glaciers of opposite orientation change in a different way. In this study, we exploit Ice Cloud and land Elevation Satellite (ICESat)/ Geoscience Laser Altimetry System (GLAS) data in combination with the NASA Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM) and the Global Land Ice Measurements from Space (GLIMS) glacier mask to estimate glacial thickness change trends between 2003 and 2009 on the whole Tibetan Plateau. The results show that 90 glacial areas could be distinguished. Most of observed glacial areas on the Tibetan Plateau are thinning, except for some glaciers in the Northwest. In general, glacial elevations on the whole Tibetan Plateau decreased at an average rate of -0.17 ± 0.47 meters per year (m a-1) between 2003 and 2009, taking together glaciers of any size, distribution, and location of the observed glacial area. Moreover, the results show that glacial elevation changes indeed strongly depend on the relative position in a mountain range.

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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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Bering Glacier surge 2011: analysis of laser altimeter data

Annals of Glaciology ◽

10.3189/2013aog63a348 ◽

2013 ◽

Vol 54 (63) ◽

pp. 158-170 ◽

Cited By ~ 7

Author(s):

Ute C. Herzfeld ◽

Brian McDonald ◽

Maciej Stachura ◽

Robert Griffin Hale ◽

Phillip Chen ◽

...

Keyword(s):

Large Scale ◽

Altimeter Data ◽

Small Scale ◽

Rapid Progression ◽

Laser Altimeter ◽

Reservoir Area ◽

Airborne Laser ◽

Bering Glacier ◽

Change Characteristics ◽

Elevation Changes

AbstractThe Bering Glacier–Bagley Icefield system in Alaska is currently surging (2011). Large-scale elevation changes and small-scale elevation-change characteristics are investigated to understand surge progression, especially mass transport from the pre-surge reservoir area to the receiving area and propagation of the kinematic surge wave as manifested in heavy crevassing characteristic of rapid, brittle deformation. This analysis is based on airborne laser altimeter data collected over Bering Glacier in September 2011. Results include the following: (1) Maximal crevasse depth is 60 m, reached in a rift that separates two deformation domains, indicative of two different flow regimes. Otherwise surge crevasse depth reaches 20–30 m. (2) Characteristic parameters of structural provinces are derived by application of geostatistical classification. Parameters include significance and spacing of crevasses, surface roughness and crevasse-edge curvature (indicative of crevasse age). A classification based on these parameters serves to objectively discriminate structural provinces, indicative of surge progression down-glacier and up-glacier. (3) Elevation changes from 2011 and 2010 altimetry show 40–70 m surface lowering in the reservoir area in lower central Bering Glacier and 20–40m thickening near the front in Tashalich arm. Combining elevation changes with results of crevasse profilometry and pattern analysis, the rapid progression of the surge can be mathematically–physically reconstructed.

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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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