Skip to main content Accessibility help
×
×
Home

The Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model

  • Almut Iken (a1)
Abstract

In order to interpret observed short-term variations of the sliding velocity of a glacier the effect of a variable subglacial water pressure on the sliding velocity has been studied using an idealized numerical model. In particular the transient stages of growing or shrinking water-filled cavities at the ice-bedrock interface were analysed. It was found that the sliding velocity was larger when cavities were growing than when they had reached the steady-state size for a given water pressure. The smallest sliding velocities occurred while cavities were shrinking. When cavitation is substantial a small drop of water pressure below the steady-state value (e.g. by 0.5 bar) can temporarily cause backward sliding. A limiting water pressure at which sliding becomes unstable is derived. The consequences of more realistic assumptions than those of the model are discussed.

Résumé

Dans le but d’interpréter les variations de vitesse à court terme qui ont été observées, on a étudié à l’aide d’un modèle numérique idéalisé l’effet exercé par une pression hydraulique sous-glaciaire variable sur la vitesse de glissement d’un glacier. On a étudié en particulier les états transitoires de la croissance et de la décroissance des poches d’eau situées à l’interface glace-bedrock. Il s’est révélé que pendant la phase de croissance des cavités, la vitesse de glissement est plus grande qu’à l’état stationnaire pour une pression hydraulique donnée. Les vitesses de glissement les plus faibles se produisent lors du rétrécissement des cavités. Lorsque le volume des cavités est suffisamment grand, une faible diminution de la pression (p.ex. de 0,5 bar) peut temporairement provoquer un glissement vers l’amont. On a déterminé une valeur limite de la pression hydraulique pour laquelle de glissement devient instable. On discute les conséquences d’hypothèses plus réalistes que celles sur lesquelles le modèle repose.

Zusammenfassung

Mit dem Ziel, beobachtete kurzzeitige Geschwindigkeits-schwankungen zu erklären, wurde der Einfluss eines veränderlichen subglazialen Wasserdruckes auf die Gleitgeschwindigkeit mit einem idealisierten numerischen Modell untersucht. Insbesondere wurden die Übergangsphasen von wachsenden oder schrumpfenden, wassergefüllten Hohlräumen an der Grenzfläche von Eis und Felsbett analysiert. Es zeigte sich, dass die Gleitgeschwindigkeit grösser war, wenn Hohlräume zu wachsen begannen, als wenn sie die für einen bestimmten Wasserdruck endgültige Grösse erreicht hatten. Die kleinsten Gleitgeschwindigkeiten kamen vor, während die Hohlräume schrumpften. Bei genügendem Ausmass der Hohlräumbildung kann ein geringfügiges Absinken des Wasserdruckes unter den Gleichgewichtswert (z.B. um 0,5 bar) vorübergehend Rückwärtsgleiten verursachen. Ein Grenzwert des Wasserdruckes, bei dem das Gleiten unstabil wird, wird hergeleitet. Die Auswirkung weniger spezieller Annahmen als derer, die dem Modell zugrundeliegen, wird diskutiert.

  • 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 Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model
      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 Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model
      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 Effect of the Subglacial Water Pressure on the Sliding Velocity of a Glacier in an Idealized Numerical Model
      Available formats
      ×
Copyright
References
Hide All
Boulton, G. S. 1979. Processes of glacier erosion on different substrata. Journal of Glaciology, Vol. 23, No. 89, p. 1538.
Boulton, G. S., and others. 1979. Direct measurement of stress at the base of a glacier, by Boulton, G. S., Morris, E. M., Armstrong, A. A., and Thomas, A.. Journal of Glaciology, Vol. 22, No. 86, p. 324.
Engelhardt, H. F., and others. 1978. Basal sliding and conditions at the glacier bed as revealed by bore-hole photography, by Engelhardt, H. F., Harrison, W. D., and Kamb, [W.] B.. Journal of Glaciology, Vol. 20, No. 84, p. 469508.
Iken, A. 1974. Glaciology, No. 5. Velocity fluctuations of an Arctic valley glacier, a study of the White Glacier, Axel Heiberg Island, Canadian Arctic Archipelago. Axel Heiberg Island Research Reports, McGill University, Montreal.
Iken, A. [1978.] Variations of surface velocities of some Alpine glaciers measured at intervals of a few hours. Comparison with Arctic glaciers, Zeitschrift für Gtetscherkunde und Glazialgeologie, Bd. 13, Ht. 1-2, 1977, p. 2335.
Jones, A. S. 1979. The flow of ice over a till bed. Journal of Glaciology, Vol. 22, No. 87. p. 393–95.
Kamb, W. B. 1970. Sliding motion of glaciers: theory and observation. Review of Geophysics and Space Physics, Vol. 8, No. 4, p. 673728.
Kamb, W. B., and others. 1979. The ice–rock interface and basal sliding process as revealed by direct observation in bore holes and tunnels, by Kamb, [W.] B., Engelhardt, H. F., and Harrison, W. D.. Journal of Glaciology, Vol. 23, No. 89, p. 416–19. [Abstract.]
Kovári, K. 1969. Ein Beitrag zum Bemessungsproblem von Untertagbauten. Schweizerische Bauzeitung. Jahrg. 87, Ht. 37, p. 687–97.
Kovári, K., and others. 1976. Parametric studies as a design aid in tunneling, by Kovári, K., Hagedorn, H., and Fritz, P.. (In Desai, C. S., ed. Numerical methods in geomechanics. Papers presented and discussed at the second International Conference on Numerical Methods in Geomechanics held at Virginia Polytechnic Institute and State University, Blacksburg, Virginia, U.S.A., in June, 1976. New York, American Society of Civil Engineers, Vol. 2, p. 77390.)
Lliboutry, L. A. 1968. General theory of subglacial cavitation and sliding of temperate glaciers. Journal of Glaciology, Vol. 7, No. 49, p. 2158.
Lliboutry, L. A. 1979. Local friction laws for glaciers: a critical review and new openings. Journal of Glaciology, Vol. 23, No. 89, p. 6795.
Morland, L. W. 1976. Glacier sliding down an inclined wavy bed. Journal of Glaciology, Vol. 17, No. 77, p. 447–62.
Nye, J. F. 1969. A calculation on the sliding of ice over a wavy surface using a Newtonian viscous approximation. Proceedings of the Royal Society of London, Ser. A, Vol. 311, No. 1506, p. 445–67.
Robin, G. de Q. 1976. Is the basal ice of a temperate glacier at the pressure melting point? Journal of Glaciology, Vol. 16, No. 74, p. 183–96.
Tyulina, T. Yu. 1976. Izmereniye otnositel’nogo peremeshcheniya l’da v sloyakh i razryvakh na lednike Marukh [On the measurements of relative ice transport in layers and faults of Lednik Marukh], Materialy Glyatsio-logicheskikh Issledovaniy. Khronika. Obsuzhdeniya, Vyp. 25, p. 105–16.
Weertman, J. 1962. Catastrophic glacier advances. Union Géodésique el Géophysique Internationale. Association Internationale d’Hydrologie Scientifique. Commission des Neiges et des Glaces. Colloque d’Obergurgl, 10–9—18–9 1962, P. 3139. (Publication No. 58 de I’Association Internationale d’Hydrologie Scientifique.)
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Glaciology
  • ISSN: 0022-1430
  • EISSN: 1727-5652
  • URL: /core/journals/journal-of-glaciology
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×

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