Sensitivity of Grounding-Line Dynamics to Viscoelastic Deformation of the Solid-Earth in an Idealized Scenario

• Main Authors: Konrad, H., Sasgen, I., Klemann, V., Thoma, M., Grosfeld, K., Martinec, Z.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2016
• Subjects: Eisschild*; Ice Sheet; Ice Shelf; Polarforschung; Schelfeis*
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_1504405; https://gfzpublic.gfz-potsdam.de/pubman/item/item_1504405_3/component/file_1577911/polfor.2016.005.pdf; https://gfzpublic.gfz-potsdam.de/pubman/item/item_1504405_3/component/file_1577912/polfor.2016.005_a.pdf

We investigate the behaviour of the grounding line (GL) of an idealised ice sheet and ice shelf by coupling a thermomechanical ice-sheet model to a self-gravitating viscoelastic solid-Earth model (SGVEM) in which a gravitationally self-consistent sea-level evolution is considered. The steadystate ice-sheet – shelf configuration is subject to forcing by sea-level rise, or altered surface mass balance and basal conditions, resulting in a retreat of the GL. We confirm previous studies showing that GL retreat can be decelerated and stopped by viscoelastic deformation of the solid Earth. We focus on the influence of lithosphere thickness and the upper mantle viscosity on the GL retreat and find that the time scales of solid-Earth relaxation, which are parameterised by the upper mantle viscosity, are most important for GL stability. We compare these retreat characteristics with results from the simpler “elastic lithosphere – relaxing asthenosphere” (ELRA) approximation of solid-Earth deformation, which is common in ice-sheet modelling. We find that the inconsistent description of sea level and the simplified relaxation behaviour of the ELRA approximation introduce an artificial bias on GL migration. Finally, we discuss the implications of similar time scales, on which ice dynamics and solid-Earth adjustment proceed, for the long-term stability of the ice sheet. Wir untersuchen das Verhalten der Aufsetzlinie eines idealisierten Eisschildes mit angrenzendem Schelfeis, indem wir ein numerisches thermomechanisches Eisschildmodell mit einem selbstgravitativen, viskoelastischen Modell für die feste Erde koppeln. In letzterem werden Meeresspiegeländerungen gravitativ konsistent berücksichtigt. Das gegebene Gleichgewicht, in welchem sich das System aus Eisschild und -schelf befindet, wird durch Anstieg des Meeresspiegels, bzw. veränderte Oberflächenmassenbilanz und basale Randbedingungen gestört, wodurch sich die Aufsetzlinie zurückzieht. Wie bereits in früheren Studien beschrieben, kann die viskoelastische Deformation der ...