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A Flow Model and a Time Scale for the Ice Core from Camp Century, Greenland

  • W. Dansgaard (a1) and S. J. Johnsen (a1)
Abstract

A flow model is described for the Camp Century area in Greenland. The horizontal velocity profile along the core is assumed to be uniform from the surface down to y = 400 m above the bottom. Below this level, the horizontal velocity v x , is assumed to decrease proportionally to y. Furthermore, at a given y, v x is assumed to be proportional to the distance x from the ice divide. The resulting vertical strain-rate under steady-state conditions gives the age of the ice as a function of y. The flow model has explained the measured temperature profile, and the time scale has been verified by comparison between observed stable isotope variations and past climatic changes (at least 70 000 years back in time) estimated by other methods.

Résumé

Les auteurs décrivent un modèle d’écoulement de la glace pour la zone du Camp Century au Groenland. Le profil horizontal des vitesses tout au mond de la carotte de glace est supposé être uniforme de la surface jusqu’à une profondeur de y = 400 m in au-dessus de socle rocheux. En-dessous de ce niveau, la vitesse horizontale v x est supposée décroître proportionnellement à y. De plus, à une profondeur y donnée. v x est supposée être proportionnelle à la distance x de la ligne de séparation des glaces. La vitesse de déformation verticale qui en résulte sous des conditions stationnaires donne l’âge de la glace en fonction de y. Le modèle d’écoulement a expliqué le profil mesuré des températures et l’échelle des temps a été vérifiée par comparaison des variations observées des concentrations d’isotope stable et les changements climatiques passées (jusqu’à 70 000 ans en arrière) estimés par d’autres méthodes.

Zusammenfassung

Für das Gebiet von Camp Century in Grönland wird ein Fliessmodell beschrieben. Das Horizontalgeschwindigkeitsprofil entlang des Kerns wird von der Oberfläche bis zu y = 400 m über dem Boden als gleichförmig angenommen. Darunter wird eine Abnahme der Horizontalgeschwindigkeit v x proportional zu y vorausgesetzt. Weiterhin wird unterstellt. dass sich für ein gegebenes y v x proportional zur Entfernung x von der Eisscheide verhält. Die resultierende vertikale Verformungsgeschwindigkeit unter stetigen Bedingungen ergibt das Alter des Eiscs als eine Funktion von y. Das Fliessmodell erklärt das gemessene Temperaturprofil: die Zeitskala wird durch einen Vergleich zwischen beobachteten Variationen stabiler Isotope und früheren Klimaschwankungen (zumindest in den letzten 70 000 Jahren), die mit anderen Methoden ahgeschätzt werden, bestätigt.

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Copyright
References
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Journal of Glaciology
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