Description: Der glazial-isostatische Ausgleich in Island infolge des rezenten Abschmelzens der Vatnajökull-Eiskappe wird durch die Viskositätsverteilung im Erdinnern und durch die Details der Abschmelzgeschichte kontrolliert. Interpretationen der Ergebnisse von GPS- und Schweremeßkampagnen im Zeitintervall 1991–2000 bzw. 1992–1999 mit Hilfe lateral homogener Erdmodelle zur Bestimmung der Lithosphärenmächtigkeit, Asthenosphärenmächtigkeit und Asthenosphärenviskosität sind bislang nicht voll zufriedenstellend gewesen. Insbesondere nahe des Eisrandes war die Anpassung der berechneten Landhebung und Schwereänderung an die Beobachtungsdaten nur unzureichend, was mit der Nichtberücksichtigung des Island-Plumes in den lateral homogenen Erdmodellen zusammenhängen kann. In der vorliegenden Arbeit wird für die Modellierung der Landhebung und Schwereänderung ein Programmpaket verwendet, daß die Berechnung auflastinduzierter Störungen eines Maxwellviskoelastischen, inkompressiblen, selbstgravitierenden, sphärischen Erdmodells gestattet. Um das Vorhandensein des Plumes unter dem Vatnajökull zu simulieren, wird eine axialsymmetrische Viskositätsverteilung verwendet, wobei der Plumeradius und die Plumeviskosität freie Parameter sind. Basierend auf seismischen Ergebnissen wird über dem Plume eine 6 km mächtige Lithosphäre angenommen, die sich im peripheren Bereich des Plumes auf 35 km verdickt. Die Abschmelzgeschichte des Vatnajökulls beruht auf Interpretationen geomorphologischer und klimatologischer Untersuchungen und wird durch eine mit dem Plume koaxiale Last mit parabolischem Profil und zeitabhängigem Radius simuliert. Die Ergebnisse der Modellierung favorisieren einen Plumeradius von ~ 80 km und eine Plumeviskosität von (0.3–1.0) × 1018 Pa s.

Description: Visual Analytics is a method that combines visualization and automated analysis in highly interactive interfaces. These systems enable geoscientists to explore their data sets, to steer the analysis process and assess results. In this article, we explain the potential of Visual Analytics with three examples that were developed at the GFZ in recent years in close cooperation between computer scientists and geoscientists. They include (1) the analysis of lake sediments to understand climate and landscape developments in the past, (2) the analysis of complex geochemical simulation models in fluid systems modeling, and (3) the validation of simulation models in Earth system modeling. The developed Visual Analytics concepts largely differ from each other due to the variety of analytical tasks and data characteristics across the applications. Nevertheless, the examples reveal common benefits of using Visual Analytics for data interpretation in geoscientific research. The method supports the full exploration of complex data sets rather than relying on small sample sets. Geoscientists can employ their expert knowledge to correctly interpret data where automatic methods alone are not sufficient. Yet, the close linking with automated methods enables the handling of large and complex data sets. In sum, the novel Visual Analytics concepts contribute to data interpretation and thereby to answering relevant geoscientific questions.

Description: The work contained in this thesis considers deformations of the Earth, which are produced by the loads of the last ice-age glacial sheets. The forces the Earth sets against the surface loads are the buoyancy force of the Earth's mantle and the opposing force by the elastic flexure of the lithosphere. Because the time scale of the ice-age of some 100,000 years is short with respect to geological time scales, the viscoelastic behaviour of the Earth has to be considered. Viscoelasticity results in a retarded response of the Earth, which is observed as postglacial uplift in previously glaciated regions, 8,000 years after deglaciation. To model the buoyancy of the Earth's mantle, often a viscous incompressible fluid of homogeneous density is assumed. More recent studies consider also compressibility of the mantle material, but keep the homogeneous density. This results in an inconsistent reference state, because the self compression due to hydrostatic pressure is neglected. These models are discussed here, and the problems are shown, which arise from the description of the field equations for a viscoelastic compressible gravitating continuum in a half-space geometry. The opposing force by the elastic flexure of the lithosphere is determined by the flexural rigidity of the lithospheric plate. If we consider viscoelastic layers in the lithosphere, the flexural rigidity is reduced. Therefore, the overall thickness of a viscoelastic layered lithosphere is much larger than its effective elastic thickness deduced from assuming one elastic plate. Consequently the effective elastic thickness looses its merit for assessing the lithosphere thickness. We show, how strong effective elastic thickness and lithosphere thickness may differ, in which way the viscoelastic structure of the Earth influences this difference for glacial loads and which consequences arise for the lithospheric stress state.