An official website of the United States government
Abstract This article presents a comprehensive benchmark study for the newly updated and publicly available finite element code CitcomSVE for modeling dynamic deformation of a viscoelastic and incompressible planetary mantle in response to surface and tidal loading. A complete description of CitcomSVE’s finite element formulation including calculations of the sea‐level change, polar wander, apparent center of mass motion, and removal of mantle net rotation is presented. The 3‐D displacements and displacement rates and the gravitational potential anomalies are solved with CitcomSVE for three benchmark problems using different spatial and temporal resolutions: (a) surface loading of single harmonics, (b) degree‐2 tidal loading, and (c) the ICE‐6G GIA model. The solutions are compared with semi‐analytical solutions for error analyses. The benchmark calculations demonstrate the accuracy and efficiency of CitcomSVE. For example, for a typical ICE‐6G GIA calculation with a 122‐ky glaciation‐deglaciation history, time increment of 100 years, and ∼50 km (or ∼0.5°) surface horizontal resolution, it takes ∼4.5 hr on 96 CPU cores to complete with about 1% and 5% errors for displacements and displacement rates, respectively. Error analyses shows that CitcomSVE achieves a second order accuracy, but the errors are insensitive to temporal resolution. CitcomSVE achieves the parallel computational efficiency >75% for using up to 6,144 CPU cores on a parallel supercomputer. With its accuracy, computational efficiency and its open‐source public availability, CitcomSVE provides a powerful tool for modeling viscoelastic deformation of a planetary mantle with 3‐D mantle viscous and elastic structures in response to surface and tidal loading problems.
more »
« less
This content will become publicly available on January 1, 2026
CitcomSVE-3.0: a three-dimensional finite-element software package for modeling load-induced deformation and glacial isostatic adjustment for an Earth with a viscoelastic and compressible mantle
Abstract. Earth and other terrestrial and icy planetary bodies deform viscoelastically under various forces. Numerical modeling plays a critical role in understanding the nature of various dynamic deformation processes. This article introduces a newly developed open-source package, CitcomSVE-3.0, which efficiently solves the viscoelastic deformation of planetary bodies. Based on its predecessor, CitcomSVE-2.1, CitcomSVE-3.0 is updated to account for three-dimensional elastic compressibility and depth-dependent density, which are particularly important in modeling horizontal displacement for viscoelastic deformation. We benchmark CitcomSVE-3.0 against a semi-analytical code for two types of loading problems: (1) single harmonic loads on the surface or as a tidal force and (2) the glacial isostatic adjustment (GIA) problem with a realistic ice sheet loading history (ICE-6G_D) and an updated version of sea level equations. The benchmark results presented here demonstrate the accuracy and efficiency of this package. CitcomSVE-3.0 shows second-order accuracy in terms of spatial resolution. For typical GIA modeling with a 122 kyr glaciation–deglaciation history, a surface horizontal resolution of ∼50 km, and a time increment of 125 years, this takes ∼3 h on 384 CPU cores to complete, with displacement rate errors of less than 5 %.
more »
« less
- PAR ID:
- 10618579
- Publisher / Repository:
- Copernicus Publications
- Date Published:
- Journal Name:
- Geoscientific Model Development
- Volume:
- 18
- Issue:
- 5
- ISSN:
- 1991-9603
- Page Range / eLocation ID:
- 1445 to 1461
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
SUMMARY Constitutive laws are a necessary ingredient in calculations of glacial isostatic adjustment (GIA) or other surface loading problems (e.g. loading by ocean tides). An idealized constitutive law governed by the Maxwell viscoelastic model is widely used but increasing attention is being directed towards more intricate constitutive laws that, in particular, include transient rheology. In this context, transient rheology collectively refers to dissipative mechanisms activated in addition to creep modelled by the Maxwell viscoelastic model. Consideration of such viscoelastic models in GIA is in its infancy and to encourage their wider use, we present constitutive laws for several experimentally derived transient rheologies and outline a flexible method in which to incorporate them into geophysical problems, such as the viscoelastic deformation of the Earth induced by surface loading. To further motivate this need, we demonstrate, via the Love number collocation method, how predictions of crustal displacement depart significantly between Earth models that adopt only Maxwell viscoelasticity and those with transient rheology. Throughout this paper, we highlight the differences in terminology and emphases between the rock mechanics, seismology and GIA communities, which have perhaps contributed towards the relative scarcity in integrating this broader and more realistic class of constitutive laws within GIA. We focus on transient rheology since the associated deformation has been demonstrated to operate on timescales that range from hours to decades. With ice mass loss enhanced at similar timescales as a consequence of anthropogenically caused climate change, the ability to model GIA with more accurate constitutive laws is an important tool to investigate such problems.more » « less
-
Abstract. Accurate glacial isostatic adjustment (GIA) modelling in the cryosphere is required for interpreting satellite, geophysical and geological recordsand for assessing the feedbacks of Earth deformation and sea-level change on marine ice-sheet grounding lines. GIA modelling in areas of active ice lossin West Antarctica is particularly challenging because the ice is underlain by laterally varying mantle viscosities that are up to several orders ofmagnitude lower than the global average, leading to a faster and more localised response of the solid Earth to ongoing and future ice-sheet retreatand necessitating GIA models that incorporate 3-D viscoelastic Earth structure. Improvements to GIA models allow for computation of the viscoelasticresponse of the Earth to surface ice loading at sub-kilometre resolution, and ice-sheet models and observational products now provide the inputs toGIA models at comparably unprecedented detail. However, the resolution required to accurately capture GIA in models remains poorly understood, andhigh-resolution calculations come at heavy computational expense. We adopt a 3-D GIA model with a range of Earth structure models based on recentseismic tomography and geodetic data to perform a comprehensive analysis of the influence of grid resolution on predictions of GIA in the AmundsenSea Embayment (ASE) in West Antarctica. Through idealised sensitivity testing down to sub-kilometre resolution with spatially isolated ice loadingchanges, we find that a grid resolution of ∼ 13 of the radius of the load or higher is required to accurately capture the elasticresponse of the Earth. However, when we consider more realistic, spatially coherent ice loss scenarios based on modern observational records andfuture ice-sheet model projections and adopt a viscoelastic Earth, we find that predicted deformation and sea-level change along the grounding lineconverge to within 5 % with grid resolutions of 7.5 km or higher, and to within 2 % for grid resolutions of 3.75 km andhigher, even when the input ice model is on a 1 km grid. Furthermore, we show that low mantle viscosities beneath the ASE lead to viscousdeformation that contributes to the instrumental record on decadal timescales and equals or dominates over elastic effects by the end of the 21stcentury. Our findings suggest that for the range of resolutions of 1.9–15 km that we considered, the error due to adopting a coarser gridin this region is negligible compared to the effect of neglecting viscous effects and the uncertainty in the adopted mantle viscosity structure.more » « less
-
Glacial isostatic adjustment (GIA) simulations using earth models that vary viscoelastic structure with depth alone cannot simultaneously fit geographic trends in the elevation of marine isotope stage (MIS) 5a relative sea level (RSL) indicators across continental North America and the Caribbean and yield conflicting estimates of global mean sea level (GMSL). We present simulations with a GIA model that incorporates three-dimensional (3-D) variation in North American viscoelastic earth structure constructed by combining high-resolution seismic tomographic imaging with a new method for mapping this imaging into lateral variations in lithospheric thickness and mantle viscosity. We pair this earth model with a global ice history based on updated constraints on ice volume and geometry. The GIA prediction provides the first simultaneous reconciliation of MIS 5a North American and Caribbean RSL highstands and strengthens arguments that MIS 5a peak GMSL reached values close to that of the Last Interglacial. This result highlights the necessity of incorporating realistic 3-D earth structure into GIA predictions with continent-scale RSL data sets.more » « less
-
Abstract Contemporary crustal uplift and relative sea level (RSL) change in Greenland is caused by the response of the solid Earth to ongoing and historical ice mass change. Glacial isostatic adjustment (GIA) models, which seek to match patterns of land surface displacement and RSL change, typically employ a linear Maxwell viscoelastic model for the Earth's mantle. In Greenland, however, upper mantle viscosities inferred from ice load changes and other geophysical phenomena occurring over a range of timescales vary by up to two orders of magnitude. Here, we use full‐spectrum rheological models to examine the influence of transient deformation within the Greenland upper mantle, which may account for these differing viscosity estimates. We use observations of shear wave velocity combined with constitutive rheological models to self‐consistently calculate mechanical properties including the apparent upper mantle viscosity and lithosphere thickness across a broad spectrum of frequencies. We find that the contribution of transient behavior is most significant over loading timescales of 102–103 years, which corresponds to the timeframe of ice mass loss over recent centuries. Predicted apparent lithosphere thicknesses are also in good agreement with inferences made across seismic, GIA, and flexural timescales. Our results indicate that full‐spectrum constitutive models that more fully capture broadband mantle relaxation provide a means of reconciling seemingly contradictory estimates of Greenland's upper mantle viscosity and lithosphere thickness made from observations spanning a range of timescales.more » « less
