Skip to main content Accessibility help
×
Home

Origin of the Basal Ice Layer from Alpine Glaciers Indicated by its Chemistry

  • R. A. Souchez (a1) and R. D. Lorrain (a1)

Abstract

The basal ice layer of Alpine glaciers, the thickness of which can reach more than one metre, generally appears as a sequence composed of layers of bubble-poor ice 0.5-3 cm thick and dirt layers containing dispersed rock fragments. Locally, debris-free bubbly ice is also present in the sequence. This basal layer exists on the lee side of rock protuberances or along the marginal part of the glacier. Three geochemical characteristics shed some light on its origin:

  • (a)The high calcium content of basal ice sliding over limestones from the north side of Glacier do Tsanfleuron can be successfully predicted from considerations of the phase relations in regelating subglacial solutions in approximate equilibrium with subglacial calcite deposits.
  • (b)The (Na + K)/(Ca+Mg) ratio of bubble-poor basal ice from Glacier de Tsijiore Nouve which flows over gneissic rocks is significantly higher than this ratio in other samples taken in the same environment (glacier ice, melt water). This may be explained by refreezing of squeezed water, the ionic composition of which is governed by selective diffusion of ions during squeezing and/or by the water being forced through mud layers as demonstrated by us at the base of Glacier d'Argentière (Souchez and Lorrain. 1975).
  • (c)The Lead-210 activity per kg of basal ice from the south side of Glacier de Tsanfleuron is greater than that of the glacier ice immediately above, which indicates that it is younger despite percolation effects. This can be explained if recent ice accretion has occurred at the base of relatively old glacier ice. Accretion of blowing snow has been found to occur under the southern margin of the glacier.

Résumé

La couche basale des glaciers alpins, dont l'épaisseur peut atteindre plus d'un mètre, se présente généralement comme une séquence composée de lits de 0.5 à 3 cm d'épaisseur de glace sans bulles et de lits de particules contenant des fragments rocheux dispersés. Localement, de la glace bullcuse sans particules apparait également dans la séquence. Cette couche basale existe à l'aval des protubérances du lit rocheux ou le long du bord du glacier Trois caractéristiques géochimiques éclairent son origine: (a) (a)la forte concentration en Ca de la glace basale du flanc nord du glacier du Tsanfleuron qui glisse sur un substratum calcaire peut être estimée de manière très satisfaisante sur base des relations de phase des eaux sous-glaciaires à partir desquelles se forment la glace basale et les précipitations calcaires qui recouvrent la roche en place. (b) (b)le rapport (Na + K)/(Ca+Mg) de la glace sans bulles du glacier de Tsijiore Nouve qui s'écoule sur des roches gneissiques est nettement plus élevé que celui de tout autre échantillon prélevé dans le même environnement (glace de glacier, eaux de fusion). La situation peut s'expliquer si l'eau exsudée subit un. effet de séparation chimique comme celui que nous avons décrit précédemment au glacier d'Argenière ou draine sélectivement les saumures, le phénomène étant gouverné par la diffusion (Souchez et Lorrain. 1975). (c) (c)l'activité du Plomb 210 par kg de glace basale du flanc droit du glacier de Tsanfleuron est plus élevée que celle de la glace de glacier située immédiatement au-dessus. Cette particularité indique, en dépit des influences rie la percolation, que la glace basale est plus jeune que la glace de glacier qui la surmonte. Ceci ne peut s'expliquer que par pénétration et métamorphisme de neige soufflée récente sous le glacier à la faveur de décollements marginaux.

Zusammenfassung

Die Eisschicht am Grunde von Alpengletschern, deren Dicke mehr als einen Meter erreichen kann, erscheint im allgemeinen als eine Folge von 0.5-3 cm dicken blasenarmen Eisschichten und hehmutzschichten, die verstreute Felsbrocken enthalten. Lokal ist auch schuttfreies, blasenreiches Eis in der Folge anzutreffen. Dièse Grundschirht tritt aufder Leeseitc von Felshindernisscn oder làngs der Randpartien der Gletscher auf. Drei geochemische Besonderheiten crhcllen ihren Ursprung in gewissem Masse: (a) (a)Der hohe Kalziumgehalt von Grundeis, das auf der Nordseite des Tsanfleuron-Gletschers iiber Kalksteineglcitet, kann erfolgreich aus der Betrachtung der Phasenbeziehungeii in wiedergefrierenden subglazialcn Losungen hergeleitel werden, die sich annahernd im Gleichgewicht mit subglazialen Kalzitablagerungen befinden. (b) (b)Das Verhâltnis von Na+ K zu Ca + Mg in blasenarmem Grundeis des Tsijiore Nouve-Gletschers, das liber Gnetisfelsen fliesst, ist betriichtlich hôhrr als das von anderen Proben, die in der Umgebung entnommen wurden (Gletschereis, Schmclzwasser). Dies kann aus dem Wiedergefricren von geprrsstem Wasser crklarl werden, dessen lonenzusammcnsctzuiig durch selektive Diffusion von austretenden lonen wahrend der Pressung und/oder durch Druckfliessen iiber Schlammschichten gesteuert wird, wic wir bereits feuher am Grunde des Glacier d'Argentière gezeigt haben (Souchez und Lorrain, 1975). (c) (c)Die Blei-210-Aktivitat pro kg Grundeis von der Sudseite des Tsanfleuron-Gletschers 1st hoher als(' die im Gletschereis, unmittelbar daruber, worau, sich trotz: der Sickerungseinflusse: dessen relative juneges Alter ergibt. Dies lasst sich daraus erklâren, dass* standig ein Aufwachsen von Eis am Grunde des relativ Gletschereises stattfand. Das Auftreten des Aufwachsen von Driftschnec wurde unter dem Sûdrand des Gletschers festgestellt.

  • 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.

      Origin of the Basal Ice Layer from Alpine Glaciers Indicated by its Chemistry
      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.

      Origin of the Basal Ice Layer from Alpine Glaciers Indicated by its Chemistry
      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.

      Origin of the Basal Ice Layer from Alpine Glaciers Indicated by its Chemistry
      Available formats
      ×

Copyright

References

Hide All
Boulton, G. S. 1970. On the origin and transport of englacial debris in Svalbard glaciers. Journal of Glaciology, Vol. 9, No. 56. p. 21329.
Clapperton, C. M. 1975. The debris content of surging glaciers in Svaibard and Iceland. Journal oj Gtecwlogy, Vol. 14, No. 72, p. 395406.,
Crozaz, G. Unpublished. Mise au point d'une méthode de datation des glaciers basée sur la radioactivité du plomb-210. [Ph.D. thesis, Université Libre de Bruxelles, 1967.]
Crozaz, G., and others, 1964. Antarctic snow chronology with Pb2I°, [by] Crozaz, G., E. [E.] Picciotto, De, W. Breuck. Journal of Geophysical Research, Vol. 69, No. 12, p. 2597604.
Gross, G. W. 1968. Some effects of trace inorganics on the ice/water system. (In Gould, R. F., ed. Trace inorgGllics in water Washington, D.C., American Chemical Society, p. 2797. (Advances in Chemistry Series 73 )).
Haeberli, W. 1976. Eistempcraturen in den Alpen. %atschift fir Gletscherkimde tad Glazialgeologie Bd II Ht. 2, 1975, p. 20320.
Hallet, B. 1976[a]. Deposits formed by subglacial precipitation of CaCO3. Geological Society of America. Bulletin, Vol. 87, No. 7, p. 100315.
Hallet, B 1976[b]. The efTect of subglacial chemical processes on glacier sliding. Journal of Glaciotogy Vol 17 No. 76, p. 20921.
Hallet, B. and others. In press. Composition of basal ice from a glacier sliding over limestones, by Hallet, B. Lorrain, R. D. and Souchez, R. A.. Geological Society of America. Bulletin.
Kamb, W. B., and LaChapelle, E. R. 1964. Direct observation of the mechanism of glacier sliding over bedrock Journal of Glaciology, Vol. 5, No. 38, p. 15972.
Kasscr, P., and Aellçn, M. 1974. Les variations des glaciers suisses 1970-1971. Publication de la Commission des Otaciers de la Société Helvétique des Sciences. Naturelles. 92e Rapport.
Lemmens, M., and Roger, M. In press. Influence of an ion exchange on dissolved load of alpine meltwaters, tarin Surface Processes.
Lliboutry, L. A. 1964–65. Traité de glaciologie. Paris, Masson et Cie. a vols.
Malo, B. A. and Baker, R. A. 1968. Cationic concentration by freezing. (In Gould, R. F., ed. Trace inorganics in water Washington, D.C., American Chemical Society, p. 14963. (Advances in Chemistry Series, 73.)
Pranti, F. S., and others. 1973. Alpine glacier studies with nuclear methods, [by] Pranti, F. A., Ambach, W. and Eisner, H.. (In [International Hydrological Decade.] The role of snow and ice in hydrology. Proceedings of the Banff symposia, September 1972.... Paris, UNESCO; Geneva, WMO; Budapest, IAHS, Vol. 1, p. 435–44. [IAHS-AISH Publication No. 107.])
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. 18396.
Souchez, R. A., and Lorrain, R. D., 1975. Chemical sorting effect at the base of an Alpine glacier. Journal of Glacwlogy, Vol. 14, No. 71, p. 26165.
Souchez, R. A., and others. 1973. Refrcezing of interstitial water in a subglacial cavity of an Alpine glacier as indicated by the chemical composition oHce, by Souchez, R. A., Lorrain, R. D. and Lemmens, M. M.. Journal oj Glacwlogy, Vol. 12, No. 66, p. 45359.
Vivian, R. 1975. Les glaciers des Alpes occidentales. Grenoble, Imprimerie Allier.
Weertman, J. 1961, Mechanism for the formation of inner moraines found near the edge of cold ice caps and ice sheets. Journal of Glaciology, Vol. 3, No. 30, p. 96578,

Origin of the Basal Ice Layer from Alpine Glaciers Indicated by its Chemistry

  • R. A. Souchez (a1) and R. D. Lorrain (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