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Stability of the Junction of an Ice Sheet and an Ice Shelf

  • J. Weertman (a1) (a2)
Abstract

An analysis is made of the steady-state size of a two-dimensional ice sheet whose base is below sea-level and which terminates in floating ice shelves. Under the assumption of perfect plasticity it is found that an ice sheet placed on a bed whose surface was initially flat cannot exist if the depth of the bed below sea-level exceeds a critical depth. If this depth is less than the critical level, the ice sheet extends out to the edge of the continental shelf. Similar results are found with more realistic assumptions about the laws governing the flow of ice. If the bed slopes away from the centre, the ice sheet can have a stable width that increases in value as the accumulation rate increases or as sea-level is lowered. It is not possible to decide whether or not the West Antarctic ice sheet is in stable equilibrium. It is entirely possible that this ice sheet is disintegrating at present, as suggested by Hughes.

On fait une analyse de la forme d’équilibre d’une calotte à deux dimensions, dont la base est au-dessus du niveau le la mer et qui se termine en glaces flottantes. Avec l’hypothese d’une plasticié parfait; on trouve qu’une calotte placée sur un lit dont la surface était initialement plate ne peut exister si la profondeur du lit en-dessous du niveau de la mer excède une profondeur critique. Si cette profondeur est moindre que le niveau critique, la calotte s’étend en dehors des limites du plateau continental. Des résultats semblables sont obtenus à partir d’hypotheses plus rèalistes, sur les lois gouvernant l’ècoulement de la glace. Si le lit plonge en s’èloignant du centre, la calotte peut avoir une largeur stable qui croît lorsque le taux d’accumulation augmente ou lorsque le niveau de la mer s’abaisse. II n’est pas possible de déceler si la calotte glaciaire de l’Ouest. Antarctique est ou non en équilibre stable. Il est tout à fait possible que cette calotte soft actuellement en tours de désintégration, comme le suggère Hughes.

Zusammenfassung

Eine Untersuchung gall der stationären Ausdehnung eines zweidimensionalen Eisschildes, dessen Basis unter dem Meeresniveau liegt and der in schwimmenden Schelfeisen endet. Unter der Voraussetzung vollkommener Plastizität wurde gefunden, dass ein Eisschild, der auf einen ursprünglich flachen Untergrund gelagert ist, nicht bestehen kann, wenn die Tiefe der Basis unter dem Meeresniveau einen kritischen Wert überschreitet. Wird dieser Wert nicht erreicht, dann dehnt sich der Eisschild bis zum Rand des Festlandsockels aus. ähnliche Ergebnisse wurden mit realistischeren Annahmen fiber die Gesetzmässigkeiten des Eisfliessens gefunden. Wenn der Untergrund vom Zentrum nach aussen hin abfällt, kann der Eisschild eine stabile Ausdehnung annehmen, die mit wachsender Akkumulation oder mit fallendem Meeresspiegel zunimmt. Es ist nicht möglich zu entscheiden, ob der Westantarktische Eisschild sich in stabilem Gleichgewicht befindet oder nicht. Es ist durchaus möglich, dass sich dieser Eisschild gegenwärtig auf löst, wie Hughes vermutet.

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References
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Budd, W. F. 1966. The dynamics of the Amery Ice Shelf. Journal of Glaciology, Vol. 6, No. 45, p. 33558.
Hughes, T. J. 1972. Is the west Antarctic ice sheet disintegrating? ISCAP [Ice Streamline Cooperative Antarctic Project] Bulletin (Ohio State University), No. 1.
Paterson, W. S. B. 1969. The physics of glaciers. Oxford, Pergamon Press. (The Commonwealth and International Library. Geophysics Division.)
Robin, G. de Q., and others. 1970. Radio echo exploration of the Antarctic ice sheet, by Robin, G. de Q., Swithinbank, C. W. M. and Smith, B. M. E. [Union Géodésique et Géophysique Internationale. Association Internationale d’Hydrologie Scientifique.] [International Council of Scientific Unions. Scientific Committee on Antarctic Research. International Association of Scientific Hydrology. Commission of Snow and Ice.] International Symposium on Antarctic Glaciological Exploration (ISAGE), Hanover, New Hampshire, U.S.A., 3–7 September 1968, p. 97115.
Thomas, R. H. 1973[a]. The creep of ice shelves: theory. Journal of Glaciology, Vol. 12, No. 64, p. 4553.
Thomas, R. H. 1973[b]. The creep of ice shelves: interpretation of observed behaviour. Journal of Glaciology, VOL 12, No. 64, p. 5570.
Weertman, J. 1957. Deformation of floating ice shelves. Journal of Glaciology, Vol. 3, No. 21, p. 3842.
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Journal of Glaciology
  • ISSN: 0022-1430
  • EISSN: 1727-5652
  • URL: /core/journals/journal-of-glaciology
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