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Influence of subglacial geology on the position of a West Antarctic ice stream from seismic observations

Nature volume 394, pages 62–65 (1998)Cite this article

Abstract

Ice streams drain much of the interior West Antarctic Ice Sheet and buffer the main ice reservoir from oceanic influences1,2. The slow-flowing interior feeds the floating Ross Ice Shelf with ice via fast-flowing ice streams3 that are believed to modulate sea-level change through their control of inland ice storage. Understanding ice-stream behaviour, and predicting the response to climate change4, requires a better knowledge of the subglacial geology5,6. It is known that a thawed ice-bed and high-pressure basal water are necessary, but not sufficient, conditions to cause ice streaming7,8. Moreover, it has been hypothesized that a soft sedimentary bed is also required, because of its intrinsic low frictional resistance to flow9, and owing to its high erodibility so as to generate till that can deform and lubricate ice motion10,11, or to bury rough features and smooth the bed for sliding. Here we use seismic observations to provide evidence that one margin of the upglacier part of an ice stream is directly above the boundary of a basin with such sedimentary fill. The ice stream is within the basin and the ice outside the basin is slow-flowing. The basin fill presents an order-of-magnitude lower frictional resistance to ice flow than the subglacial material outside the basin. We conclude that the ice stream position is dependent on subglacial geology.

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Figure 1: Location map showing the ice stream boundaries and the experiment profile line, together with ice flow speeds and ice thickness along that line.
Figure 2: Common shot gather for a shot at SP = Km 51.0.
Figure 3: Mean residuals 〈δ(SP,Δ)〉 = tmod − tr between the model and the data are plotted at the shotpoint (SP).
Figure 4: The final models from the ice/sediment/basement model-inversions.

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Acknowledgements

We thank A. M. Smith, the British Antarctic Survey, S. Saustrup, UNAVCO, ASA, VXE-6, Fjord Instruments, and Landmark Graphics for assistance. We thank the US National Science Foundation for financial support.

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Authors and Affiliations

  1. Earth System Science Center and Department of Geosciences, Pennsylvania State University, University Park, 16802, Pennsylvania, USA

    S. Anandakrishnan & R. B. Alley

  2. Institute for Geophysics, University of TexasAustin, Austin, 78759, Texas, USA

    D. D. Blankenship & P. L. Stoffa

Authors
  1. S. Anandakrishnan
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  2. D. D. Blankenship
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  3. R. B. Alley
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  4. P. L. Stoffa
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Correspondence to S. Anandakrishnan.

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Anandakrishnan, S., Blankenship, D., Alley, R. et al. Influence of subglacial geology on the position of a West Antarctic ice stream from seismic observations. Nature 394, 62–65 (1998). https://doi.org/10.1038/27889

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