Skip to main content Accessibility help
×
Home

The role of the margins in the dynamics of an active ice stream

  • K. A. Echelmeyer (a1), W. D. Harrison (a1), C. Larsen (a1) and J. E. Mitchell (a1)

Abstract

A transverse profile of velocity was measured across Ice Stream B, West Antarctica, in order to determine the role of the margins in the force balance of an active ice stream. The profile extended from near the ice-stream center line, through a marginal shear zone and on to the slow-moving ice sheet. The velocity profile exhibits a high degree of shear deformation within a marginal zone, where intense, chaotic crevassing occurs. Detailed analysis of the profile, using analytical and numerical models of ice flow, leads to the following conclusions regarding the roles of the bed and the margins in ice-stream dynamics:

  • (i)The overall resistive drag on the ice stream is partitioned nearly equally between the margins and the bed and, thus, both are important in the force balance of the ice stream.
  • (ii)The ice within the chaotic zone must be about 10 times softer than the ice in the central part of the ice stream.
  • (iii)The average basal shear stress is 0.06 × 105 Pa. This implies that the entire bed cannot be blanketed by the weak, deformable till observed by Engelhardt and others (1990) near the center of the ice stream — there must be regions of increased basal drag.
  • (iv)High strain rates and shear stresses in the marginal zones indicate that strain heating in the margins may be significant.

While the exact quantitative values leading to these conclusions are somewhat model and location-dependent, the overall conclusions are robust. As such, they are likely to have importance for ice-stream dynamics in general.

  • 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.

      The role of the margins in the dynamics of an active ice stream
      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.

      The role of the margins in the dynamics of an active ice stream
      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.

      The role of the margins in the dynamics of an active ice stream
      Available formats
      ×

Copyright

References

Hide All
Alley,, R.B. Blankenship,, D.D., Bentley,, C.R. and Rooney,, S.T. 1987. Till beneath Ice Stream B. 3. Till deformation: evidence and implications. J.Geophys. Res., 92 (B9), 89218929.
Bentley,, C.R. 1987. Antarctic ice streams: a review. J. Geophys. Res., 92(B9), 88438858.
Bindschadler,, R. Α., Stephenson,, S.N. MacAyeal,, D.R. and Shabtaie, S. 1987.Ice dynamics at the mouth of Ice Stream B, Antarctica. J. Geophys. Res., 92 (B9), 88858894.
Blankenship,, D.D. Bentley,, C.R. Rooney,, S.T. and Alley,, R.B. 1987. Till beneath Ice Stream B. 1. Properties derived from seismic travel times. J. Geophys. Res., 92(B9), 89038911.
Clarke,, T.S. and Echelmeyer,, K. 1989. High resolution seismic reflection profiles across Jakobshavns Isbrae, Greenland. EOS, 70 43, 1080.
Echelmeyer,, K. 1983. Response of Blue Glacier to a perturbation in ice thickness: theory and observation. (Ph.D. thesis, California Institute of Technology.)
Echelmeyer,, K. Wade,, R. and Iken,, A. 1991. Mechanisms of ice stream motion: Jakobshavns Isbra, Greenland. EOS, 72 44, 150.
Echelmeyer,, K. Harrison,, W.D. Clarke,, T.S. and Benson., C. 1992. Surficial glaciology of Jakobshavns Isbrae, West Greenland: Part II. Ablation, accumulation and temperature. J. Glaciot., 38 128, 169181.
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.
Frolich,, R.M. and Doake., C. S. M. 1988. Relative importance of lateral and vertical shear on Rutford Ice Stream, Antarctica. Ann. Glaciol., 11, 1922.
Hughes,, T. 1975. The West Antarctic ice sheet: instability, disintegration, and initiation of ice ages. Rev. Geophys. Space Phys., 13 4, 502526.
Jacka,, T.H. and Budd,, W.F. 1989. Isotropic and anisotropic flow relations for ice dynamics. Ann. Glaciol., 12, 8184.
Jackson,, M. 1991. Repeat aerial photogrammetry of Ice Stream B, West Antarctica. (M.Sc. thesis, Ohio State University.)
Kamb,, B. 1991. Rheological nonlinearity and flow instability in the deforming bed mechanism of ice stream motion. J.Geophys. Res., 96(B10), 16, 58516, 595.
Kamb,, W.B. and 7 others. 1985. Glacier surge mechanism: 1982-1983 surge of Variegated Glacier, Alaska. Science, 227 4686, 469479.
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), 40711087.
MacAyeal,, D.R. 1992. The basal stress distribution of Ice Stream E, Antarctica, inferred by control methods. J. Geophys. Res., 97 (B1), 595603.
McIntyre,, N.F. 1985. The dynamics of ice-sheet outlets. J. Glaciol., 31 108, 99107.
Nye,, J.F. 1965. The flow of a glacier in a channel of rectangular, elliptic or parabolic cross-section. J. Glaciol., 5 41, 661690.
Paterson,, W.S. B. 1981. The physics of glaciers. Second edition. Oxford, etc., Pergamon Press.
Retzlaff,, R. Lord,, N. and Bentley,, C.R. 1993. Airborne-radar studies: Ice Streams A, B and C, West Antarctica. J. Glaciol., 39 133, 495506.
Shabtaie,, S. and Bentley,, C.R. 1987. West Antarctic ice streams draining into the Ross Ice Shelf: configuration and mass balance. J. Geophys. Res., 92 (B2), 13111336.
Shabtaie,, S. and Bentley,, C.R. 1988. Ice-thickness map of the West Antarctic ice streams by radar sounding. Am. Glaciol., 11, 126136.
Shabtaie,, S. Whillans, I.M. and Bentley, C.R. 1987. The morphology of Ice Streams A, B, and C, West Antarctica, and their environs. J. Geophys. Res., 92 (B9), 88658883.
Van der Veen,, C.J. and Whillans,, I.M. 1989. Force budget: II. Application to two-dimensional flow along Byrd Station Strain Network, Antarctica. J. Glaciol., 35 119, 6167.
Vornberger,, P. L. and Whillans,, I.M. 1986. Surface features of Ice Stream B, Marie Byrd Land, West Antarctica. Ann. Glaciol., 8, 168170.
Vornberger,, P.L. and Whillans,, I.M. 1990. Crevasse deformation and examples from Ice Stream B, Antarctica. J. Glaciol., 36 122, 310.
Whillans,, I.M. 1987. Force budget of ice sheets. In Van der Veen, J. and Oerlemans,, J., eds. Dynamics of the West Antarctic ice sheet. Dordrecht, etc., D. Reidel Publishing Co., 1736.
Whillans,, I.M. Bolzan,, I.M.J. and Shabtaie, S. 1987. Velocity of Ice Streams B and C, Antarctica. J. Geophys. Res., 92 (B9), 88958902.
Whillans,, I.M. Jackson, M. and Tseng, Y.-H. 1993. Velocity pattern in a transect across Ice Stream B, Antarctica. J. Glaciol., 39 133, 562572.

The role of the margins in the dynamics of an active ice stream

  • K. A. Echelmeyer (a1), W. D. Harrison (a1), C. Larsen (a1) and J. E. Mitchell (a1)

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