scholarly journals Changes in the configuration of ice stream flow from the West Antarctic Ice Sheet

1996 ◽  
Vol 101 (B3) ◽  
pp. 5499-5504 ◽  
Author(s):  
Robert W. Jacobel ◽  
Theodore A. Scambos ◽  
Charles F. Raymond ◽  
Anthony M. Gades
Keyword(s):  
Stream Flow ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream

scholarly journals Velocity Patterns and Elevations On Ice Stream B

1990 ◽  
Vol 14 ◽  
pp. 341
Author(s):  
M. Jackson ◽  
I.M. Whillans
Keyword(s):  
Longitudinal Velocity ◽  
Ice Sheet ◽  
Main Body ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Aerial Photogrammetry ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Stream B

All of the West Antarctic ice sheet draining into the Ross Ice Shelf lies on bedrock which is below sea level. This is thought to make it especially senstitive to rapid decay which could be triggered by an increase in atmospheric CO2 levels, ice stream B, one of the main outlets of the West Antarctic Ice Sheet, is thinning, possibly in response to changes in climate. However, Ice Stream C, its neighbor, is thickening. One of the most effective ways to study ice streams is by repeat aerial photogrammetry. Thousands of velocity values and elevations are available for Ice Stream B using this technique. Two sections of the ice stream have repeat photogrammetry with control. Maps of elevations, velocity components and velocity gradients have been produced following the methods of Brecher (1986). The area considered here is a 40 by 30 km block across a part of the ice stream. The maps show that most of the increase in longitudinal velocity occurs within about 6 km of the ice-stream margin and reaches a maximum of 460 m a-1 in the center of the stream. Strain rates in the shear margins reach 0.12 a-;1 and are an order of magnitude less in the main body of the stream. The elevation maps show ridges and troughs. These features appear to be related to transverse velocities.

scholarly journals Thermal regime and dynamics of the West Antarctic ice sheet

2004 ◽  
Vol 39 ◽  
pp. 85-92 ◽  
Author(s):  
Hermann Engelhardt
Keyword(s):  
Basal Layer ◽  
Ice Sheet ◽  
Ice Streams ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Kamb Ice Stream

AbstractThe temperature–depth profiles measured in 22 boreholes drilled on the West Antarctic ice sheet exhibit two distinctly different thermal states of its basal ice. The warm state shows on Siple Dome and on Whillans Ice Stream. A relatively colder state, found at the Unicorn, Kamb Ice Stream (former Ice Stream C) and Bindschadler Ice Stream (former Ice Stream D), has basal temperature gradients greater than 50 K km–1. A large block of cold ice stranded and frozen to the bed at the Unicorn and simultaneously much warmer ice existing only a few kilometers across the Dragon shear margin in fast-moving Alley Ice Stream (former Ice Stream B2) poses a paradox. The relatively cold ice at the Unicorn must have come from a source different from the present Whillans Ice Stream catchment area. It is hypothesized that the Unicorn paradox was created by a super-surge. Also, the stagnant Siple Ice Stream, many relict shear margins, cold patches of ice at the Crary Ice Rise, ice rafts embedded in the Ross Ice Shelf, all point to a major event triggered either by an internal instability or by a subareal volcanic eruption. Most of these features appeared to have been formed about 500 years ago. Subsequent freeze-on of a 10–20m thick basal layer of debris-laden ice and water loss caused a slowdown of ice streams and, in the case of Kamb Ice Stream, an almost complete stoppage.

scholarly journals Velocity Patterns and Elevations On Ice Stream B

1990 ◽  
Vol 14 ◽  
pp. 341-341
Author(s):  
M. Jackson ◽  
I.M. Whillans
Keyword(s):  
Longitudinal Velocity ◽  
Ice Sheet ◽  
Main Body ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Aerial Photogrammetry ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Stream B

All of the West Antarctic ice sheet draining into the Ross Ice Shelf lies on bedrock which is below sea level. This is thought to make it especially senstitive to rapid decay which could be triggered by an increase in atmospheric CO2 levels, ice stream B, one of the main outlets of the West Antarctic Ice Sheet, is thinning, possibly in response to changes in climate. However, Ice Stream C, its neighbor, is thickening.One of the most effective ways to study ice streams is by repeat aerial photogrammetry. Thousands of velocity values and elevations are available for Ice Stream B using this technique. Two sections of the ice stream have repeat photogrammetry with control. Maps of elevations, velocity components and velocity gradients have been produced following the methods of Brecher (1986).The area considered here is a 40 by 30 km block across a part of the ice stream. The maps show that most of the increase in longitudinal velocity occurs within about 6 km of the ice-stream margin and reaches a maximum of 460 m a-1 in the center of the stream. Strain rates in the shear margins reach 0.12 a-;1 and are an order of magnitude less in the main body of the stream.The elevation maps show ridges and troughs. These features appear to be related to transverse velocities.

scholarly journals Distribution of basal melting and freezing beneath tributaries of Ice Stream C: implication for the Holocene decay of the West Antarctic ice sheet

2003 ◽  
Vol 36 ◽  
pp. 273-282 ◽  
Author(s):  
Stefan W. Vogel ◽  
Slawek Tulaczyk ◽  
Ian R. Joughin
Keyword(s):  
Ice Sheet ◽  
Ice Streams ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
The Holocene ◽  
West Antarctic ◽  
Basal Ice ◽  
Ice Stream ◽  
Basal Melting

AbstractIce-stream tributaries connect the relatively slow-moving interior of the West Antarctic ice sheet (WAIS) with the fast-flowing Siple Coast ice streams. Basal water underneath these ice streams reduces basal resistance and enables the fast motion of the ice. Basal melting being the only source for this water, it is important to include the distribution of basal melting and freezing into numerical models assessing the stability of the WAIS. However, it is very difficult to constrain its distribution from existing field observations. Past borehole observations confirmed the presence of a wet bed at Byrd Station in the WAIS interior and at different locations within Siple Coast ice streams. However, the recent discovery of a 12–25m thick sediment-laden bubble-free basal ice layer at the UpC boreholes indicates that basal freezing is either currently occurring or had occurred upstream during the last glacial–interglacialcycle.We use a flowline model of ice thermodynamics to assess and quantify the spatial and temporal distribution of basal melting and freezing beneath Ice Stream C tributaries, taking into account the geothermal flux, shear heating and heat conduction away from the bed. Under the assumption that the ice was moving over a weak bed (τb =1–10 kPa) our model is able to reproduce a layer of frozen-on ice similar in thickness to the UpC “sticky spot” basal ice layer. Increased basal melting in the early Holocene possibly could have initiated the Holocene decay of the WAIS, whereas increased freezing rates over the past few thousand years could have decreased the amount of basal water in the system, resulting in a strengthening of the bed. This is consistent with current force-budget calculations for ice-stream tributaries and with observed stoppages and slow-downs of ice streams.

scholarly journals Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

2014 ◽  
Vol 26 (6) ◽  
pp. 674-686 ◽  
Author(s):  
C.J. Fogwill ◽  
C.S.M. Turney ◽  
N.R. Golledge ◽  
D.H. Rood ◽  
K. Hippe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Last Deglaciation ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Sheet Modelling

AbstractDetermining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity.

Grounding-line retreat of the West Antarctic Ice Sheet from inner Pine Island Bay

Geology ◽  
2012 ◽  
Vol 41 (1) ◽  
pp. 35-38 ◽  
Author(s):  
C.-D. Hillenbrand ◽  
G. Kuhn ◽  
J. A. Smith ◽  
K. Gohl ◽  
A. G. C. Graham ◽  
...  
Keyword(s):  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Grounding Line

scholarly journals A Potential Disintegration of the West Antarctic Ice Sheet: Implications for Economic Analyses of Climate Policy

2016 ◽  
Vol 106 (5) ◽  
pp. 607-611 ◽  
Author(s):  
Delavane Diaz ◽  
Klaus Keller
Keyword(s):  
Climate Policy ◽  
Expert Knowledge ◽  
Ice Sheet ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Threshold Response ◽  
West Antarctic ◽  
Climate Forcings ◽  
Economic Analyses

The Earth system may react in a nonlinear threshold response to climate forcings. Incorporating threshold responses into integrated assessment models (IAMs) used for climate policy analysis poses nontrivial challenges, for example due to methodological limitations and pervasive deep uncertainties. Here we explore a specific threshold response, a potential disintegration of the West Antarctic Ice Sheet (WAIS). We review the current scientific understanding of WAIS, identify methodological and conceptual issues, and demonstrate avenues to address some of them through a stochastic hazard IAM framework combining emulation, expert knowledge, and learning. We conclude with a discussion of challenges and research needs.

scholarly journals Simultaneous solution for mass trends on the West Antarctic Ice Sheet

2014 ◽  
Vol 8 (3) ◽  
pp. 2995-3035 ◽  
Author(s):  
N. Schön ◽  
A. Zammit-Mangion ◽  
J. L. Bamber ◽  
J. Rougier ◽  
T. Flament ◽  
...  
Keyword(s):  
Mass Loss ◽  
Antarctic Peninsula ◽  
Ice Sheet ◽  
The West ◽  
Spatial Error ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
The Antarctic

Abstract. The Antarctic Ice Sheet is the largest potential source of future sea-level rise. Mass loss has been increasing over the last two decades in the West Antarctic Ice Sheet (WAIS), but with significant discrepancies between estimates, especially for the Antarctic Peninsula. Most of these estimates utilise geophysical models to explicitly correct the observations for (unobserved) processes. Systematic errors in these models introduce biases in the results which are difficult to quantify. In this study, we provide a statistically rigorous, error-bounded trend estimate of ice mass loss over the WAIS from 2003–2009 which is almost entirely data-driven. Using altimetry, gravimetry, and GPS data in a hierarchical Bayesian framework, we derive spatial fields for ice mass change, surface mass balance, and glacial isostatic adjustment (GIA) without relying explicitly on forward models. The approach we use separates mass and height change contributions from different processes, reproducing spatial features found in, for example, regional climate and GIA forward models, and provides an independent estimate, which can be used to validate and test the models. In addition, full spatial error estimates are derived for each field. The mass loss estimates we obtain are smaller than some recent results, with a time-averaged mean rate of −76 ± 15 GT yr−1 for the WAIS and Antarctic Peninsula (AP), including the major Antarctic Islands. The GIA estimate compares very well with results obtained from recent forward models (IJ05-R2) and inversion methods (AGE-1). Due to its computational efficiency, the method is sufficiently scalable to include the whole of Antarctica, can be adapted for other ice sheets and can easily be adapted to assimilate data from other sources such as ice cores, accumulation radar data and other measurements that contain information about any of the processes that are solved for.

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