Skip to main content Accessibility help
×
Home

Basal sliding of Ice Stream B, West Antarctica

  • Engelhardt Hermann (a1) and Kamb Barclay (a1)

Abstract

A “tethered stake” apparatus is used to measure basal sliding in a borehole on Ice Stream B, West Antaretica, about 300 km upstream (east) from its grounding line near the head of the Ross Ice Shelf. A metal stake, emplaced at the top of a laver of unfrozen till underlying the ice, is connected by a tether line to a metering unit that measures the tether line as it is pulled out from the borehole by the stake as a result of basal sliding. The measured sliding motion includes any actual slip across the ice–till interface and may include in addition a possible contribution from shear deformation of till within about 3 cm of the interface. This 3 cm figure follows from a qualitative model of the movements of the stake in the course of the experiment, based on features of the record of apparent sliding. Alternative but less likely models would increase the figure from 3 cm to 10 cm or 25 cm. In any case it is small compared to the seismically inferred till thickness of 9 m. Measured apparent sliding averages 69% of the total motion of 1.2 m d−1 over 26 days of observation if a 3.5 day period of slow apparent sliding (8% of the total motion) is included in the average. The occurrence of the slow period raises the possibility that the sliding motion switches back and forth between c.80% and c. 8% of the total motion, on a time-scale of a few days. However, it is likely that the period of slow apparent sliding represents instead a period when the stake got caught on the ice sole. If the slow period is therefore omitted, the indicated average basal sliding rate is 83% of the total motion. In either case, basal sliding predominates as the cause of the rapid ice-stream motion. In the last 2 days of observation the average apparent sliding rate reached 1.17 m d−1, essentially 100% of the motion of the ice stream. If till deformation contributes significantly to the ice-stream motion, the contribution is concentrated in a shear zone 3 cm to possibly 25 cm thick at the top of the 9 m thick till layer. These observations, if applicable to the West Antaretic ice sheet in general, pose complications in modeling the rapid ice-streaming motion.

  • View HTML
    • Send article to Kindle

      To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

      Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

      Find out more about the Kindle Personal Document Service.

      Basal sliding of Ice Stream B, West Antarctica
      Available formats
      ×

      Send article to Dropbox

      To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

      Basal sliding of Ice Stream B, West Antarctica
      Available formats
      ×

      Send article to Google Drive

      To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

      Basal sliding of Ice Stream B, West Antarctica
      Available formats
      ×

Copyright

References

Hide All
Alley, R. B. 1989. Water-pressure coupling of sliding and bed deformation: II. Velocity–depth profiles. J. Glaciol., 35(119), 119129.
Alley, R. B. 1990. West Antarctic collapse—how likely? Episodes, 13(4), 231238.
Alley, R. B. and MacAyeal, D. R.. 1993. West Antarctic ice sheet collapse: chimera or clear danger? Antarct. J. U.S., 28(5), 5960.
Alley, R. B., Blankenship, D. D., Bentley, C. R. and Rooney, S.T.. 1986. Deformation of till beneath Ice Stream B, West Antarctica. Nature, 322(6074), 5759.
Alley, R. B., Blankenship, D. D., Rooney, S.T. and Bentley, C. R.: 1987. Till beneath Ice Stream B. 4. A coupled ice–till flow model. J. Geophys. Res., 92(B9), 89318940.
Alley, R. B., Blankenship, D. D., Rooney, S. T. and Bentley, C. R.. 1989. Water-pressure coupling of sliding and bed deformation: III. Application to Ice Stream B, Antarctica. J. Glaciol., 35(1l9), 130139.
Anonymous. 1997. Electronic components catalog No.115. Chicago, IL, Newark Electronics Co.
Bentley, C. R. 1987. Antarctic ice streams: a review. J. Geophys. Res., 92(B9), 88438858.
Bindschadler, R. A. ed. 1991. West Antarctic Ice Sheet Initiative. Volume 1. Science and implementation plan. Washington, DC, National Aeronautics and Space Administration. (NASA CP-3115.)
Bindschadler, R. A. and Scambos, T. A.. 1991. Satellite-image-derived velocity field of an Antarctic ice stream. Science, 252(5003), 242246.
Blake, E., Clarke, G. K. C. and Gérin, M. C.. 1992. Tools for examining subglacial bed deformation. J. Glaciol., 38(130), 388396.
Blake, E. W., Fischer, U. H. and Clarke, G. K. C.. 1994. Direct measurement of sliding at the glacier bed. J Glaciol., 40(136), 595599.
Echelmeyer, K. A., Harrison, W. D., C. Larsen and Mitchell, J. E.. 1994. The role of the margins in the dynamics of an active ice stream. J. Glaciol., 40(136), 527538.
Engelhardt, H. and Kamb, B.. 1997. Basal hydraulic system of a West Antarctic ice stream: constraints from borehole observations. J. Glaciol., 43(144), 207230.
Engelhardt, H. F., Harrison, W. D. and B. Kamb. 1978. Basal sliding and conditions at the glacier bed as revealed by bore-hole photography. J. Glaciol., 20(84), 469508.
Engelhardt, H., Humphrey, N., Kamb, B. and Fahnestock, M.. 1990. Physical conditions at the base of a fast moving Antarctic ice stream. Science, 248(4951), 5759.
Hulbe, C. L. 1994. Flow of Ice Stream B, West Antarctica, and a method for determining ice thickness change at remote locations using differential GPS. (M.Sc. thesis, Ohio State University.)
Jackson, M. and Kamb, B.. 1997. The marginal shear stress of Ice Stream B, West Antarctica. J. Glaciol., 43(145), 415426.
Kamb, B. 1991. Rheological nonlinearity and flow instability in the deforming bed mechanism of ice stream motion. J. Geophys. Res., 96(B10), 16,685–16,595.
MacAyeal, D. R. 1989. Large-scale ice flow over a viscous basal sediment: theory and application to Ice Stream B, Antarctica. J. Geophys. Res., 94(B4), 40714087.
MacAyeal, D. R. 1992. Irregular oscillations of the West Antarctic ice sheet. Nature, 359(6390), 2932.
Paterson, W S. B. 1994. The physics of glaciers. Third edition. Oxford, etc., Elsevier.
Robin, G. de Q. 1986. Fast glacier flow: a soft bed is not the whole answer. Nature, 323(6088), 490491.
Rooney, S. T., Blankenship, D. D., Alley, R. B. and Bentley, C. R.. 1987. Till beneath Ice Stream B. 2. Structure and continuity. J. Geophys. Res., 92(B9), 89138920.
Rose, K. E. 1979. Characteristics of ice flow in Marie Byrd Land, Antarctica. J. Glaciol., 24(90), 6375.
Tulaczyk, S., Kamb, B., Scherer, R. P. and Engelhardt, H. F.. In press. Sedimentary processes at the base of West Antarctic ice stream: constraints from textural and compositional properties of subglacial debris. Journal of Sedimentary Research.
Whillans, I. M. and C. J. van derVeen. 1993. New and improved determinations of velocity of Ice Streams B and C, West Antarctica. J. Glaciol., 39(133), 483490.
Whillans, L. M., Bolzan, J. and Shabtaie, S.. 1987. Velocity of Ice Streams B and C, Antarctica. J Geophys. Res., 92(B9), 88958902.

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed