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  • English  (4)
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  • 1
    Monograph available for loan
    Monograph available for loan
    The geochemistry and geophysics of the Antarctic mantle (2023)
    London : The Geological Society
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    Call number: 9/M 24.95579
    In: Geological Society memoir
    Type of Medium: Monograph available for loan
    Pages: 361 Seiten , Illustrationen, Karten, Diagramme
    ISBN: 978-1-78620-467-7
    Series Statement: Geological Society Memoir 56
    Language: English
    Location: Reading room
    Branch Library: GFZ Library
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  • 2
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    A benchmark study of the sea-level equation in GIA modelling (2017)
    In:  Geophysical Research Abstracts Vol. 19, EGU2017-8681
    Details
    Publication Date: 2020-02-12
    Description: The sea-level load in glacial isostatic adjustment (GIA) is described by the so called sea-level equation (SLE), which represents the mass redistribution between ice sheets and oceans on a deforming earth. Various levels of complexity of SLE have been proposed in the past, ranging from a simple mean global sea level (the so-called eu- static sea level) to the load with a deforming ocean bottom, migrating coastlines and a changing shape of the geoid. Several approaches to solve the SLE have been derived, from purely analytical formulations to fully numerical methods. Despite various teams independently investigating GIA, there has been no systematic intercomparison amongst the solvers through which the methods may be validated. The goal of this paper is to present a series of benchmark experiments designed for testing and comparing numerical implementations of the SLE. Our approach starts with simple load cases even though the benchmark will not result in GIA predictions for a realistic loading scenario. In the longer term we aim for a benchmark with a realistic loading scenario, and also for benchmark solutions with rotational feedback. The current benchmark uses an earth model for which Love numbers have been computed and benchmarked in Spada et al (2011). In spite of the significant differences in the numerical methods employed, the test computations performed so far show a satisfactory agreement between the results provided by the participants. The differences found can often be attributed to the different approximations inherent to the various algorithms.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 3
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    Ice sheet – solid earth feedback during the last glacial cycle in Antarctica and Greenland (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-29
    Description: The solid earth influences ice sheet dynamics by controlling bedrock deformation and hence surface elevation and grounding line position. These in turn determine surface and basal melt. Ice-sheet models typically include models to compute bedrock deformation with a constant mantle viscosity (or similar parameter), whereas mantle viscosity can vary strongly underneath the ice sheets. Here we use a recently developed model that couples an ice-sheet model (ANICE) to a finite-element based GIA model that includes 3D variations in viscosity derived from seismic measurements. We investigate the effect of mantle viscosity variations on the evolution of the last glacial ice sheets in Antarctica and Greenland. In Antarctica, the main feedback mechanism is the effect of bedrock elevation on local sea level and grounding line position. In particular, uplifting bedrock in marine ice sheets reduces ice sheet loss during deglaciation. Results show a grounding line position that is 500 km more outwards when including 3D variations in mantle viscosity compared to a homogeneous viscosity. In Greenland, the main feedback is the effect of bedrock elevation on the surface elevation and hence surface melt. We show that this feedback mainly manifests in north-west Greenland where the mantle viscosity is above average. The higher mantle viscosity leads to higher ice sheet elevation at last glacial maximum, which leads to less surface melt during deglaciation. The results underline the importance of including 3D viscosity in modeling ice sheet evolution.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
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    A commercial finite element approach to modelling Glacial Isostatic Adjustment on spherical self-gravitating compressible earth models (2023)
    In:  Geophysical Journal International
    Details
    Publication Date: 2023-10-25
    Description: This paper presents a method that modifies commercial engineering-oriented finite element packages for the modelling of Glacial Isostatic Adjustment (GIA) on a self-gravitating, compressible and spherical Earth with 3-D structures. The approach, called the iterative finite element body and surface force (FEMIBSF) approach, solves the equilibrium equation for deformation using the ABAQUS finite element package and calculates potential perturbation consistently with finite element theory, avoiding the use of spherical harmonics. The key to this approach lies in computing the mean external body forces for each finite element within the Earth and pressure on Earth's surface and core–mantle boundary (CMB). These quantities, which drive the deformation and stress perturbation of GIA but are not included in the equation of motion of commercial finite element packages, are implemented therein. The method also demonstrates how to calculate degree-1 deformation directly in the spatial domain and Earth-load system for GIA models. To validate the FEMIBSF method, loading Love numbers (LLNs) for homogeneous and layered earth models are calculated and compared with three independent GIA methodologies: the normal-mode method, the iterative body force method and the spectral-finite element method. Results show that the FEMIBSF method can accurately reproduce the unstable modes for the homogeneous compressible model and agree reasonably well with the Love number results from other methods. It is found that the accuracy of the FEMIBSF method increases with higher resolution, but a non-conformal mesh should be avoided due to creating the so-called hanging nodes. The role of a potential force at the CMB is also studied and found to only affect the long-wavelength surface potential perturbation and deformation in the viscous time regime. In conclusion, the FEMIBSF method is ready for use in realistic GIA studies, with modelled vertical and horizontal displacement rates in a disc load case showing agreement with other two GIA methods within the uncertainty level of GNSS measurements.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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