A new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data

2004 ◽  
Vol 225 (1-2) ◽  
pp. 177-189 ◽  
Author(s):  
J.X. Mitrovica ◽  
A.M. Forte
Keyword(s):  
Joint Inversion ◽  
Glacial Isostatic Adjustment ◽  
Isostatic Adjustment ◽  
Mantle Viscosity

scholarly journals Lithosphere and upper-mantle structure of the southern Baltic Sea estimated from modelling relative sea-level data with glacial isostatic adjustment

Solid Earth ◽  
2014 ◽  
Vol 5 (1) ◽  
pp. 447-459 ◽  
Author(s):  
H. Steffen ◽  
G. Kaufmann ◽  
R. Lampe
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Upper Mantle ◽  
Glacial Isostatic Adjustment ◽  
Relative Sea Level ◽  
Southern Baltic Sea ◽  
Lithospheric Thickness ◽  
Isostatic Adjustment ◽  
Mantle Viscosity ◽  
Ice Model

Abstract. During the last glacial maximum, a large ice sheet covered Scandinavia, which depressed the earth's surface by several 100 m. In northern central Europe, mass redistribution in the upper mantle led to the development of a peripheral bulge. It has been subsiding since the begin of deglaciation due to the viscoelastic behaviour of the mantle. We analyse relative sea-level (RSL) data of southern Sweden, Denmark, Germany, Poland and Lithuania to determine the lithospheric thickness and radial mantle viscosity structure for distinct regional RSL subsets. We load a 1-D Maxwell-viscoelastic earth model with a global ice-load history model of the last glaciation. We test two commonly used ice histories, RSES from the Australian National University and ICE-5G from the University of Toronto. Our results indicate that the lithospheric thickness varies, depending on the ice model used, between 60 and 160 km. The lowest values are found in the Oslo Graben area and the western German Baltic Sea coast. In between, thickness increases by at least 30 km tracing the Ringkøbing-Fyn High. In Poland and Lithuania, lithospheric thickness reaches up to 160 km. However, the latter values are not well constrained as the confidence regions are large. Upper-mantle viscosity is found to bracket [2–7] × 1020 Pa s when using ICE-5G. Employing RSES much higher values of 2 × 1021 Pa s are obtained for the southern Baltic Sea. Further investigations should evaluate whether this ice-model version and/or the RSL data need revision. We confirm that the lower-mantle viscosity in Fennoscandia can only be poorly resolved. The lithospheric structure inferred from RSES partly supports structural features of regional and global lithosphere models based on thermal or seismological data. While there is agreement in eastern Europe and southwest Sweden, the structure in an area from south of Norway to northern Germany shows large discrepancies for two of the tested lithosphere models. The lithospheric thickness as determined with ICE-5G does not agree with the lithosphere models. Hence, more investigations have to be undertaken to sufficiently determine structures such as the Ringkøbing-Fyn High as seen with seismics with the help of glacial isostatic adjustment modelling.

Parameters controlling mid-Holocene highstand in Glacial Isostatic Adjustment modelling

2021 ◽  
Author(s):  
Tanghua Li ◽  
Stephen Chua ◽  
Nicole Khan ◽  
Patrick Wu ◽  
Benjamin Horton
Keyword(s):  
Southeast Asia ◽  
Sea Level ◽  
Late Holocene ◽  
Ice Sheets ◽  
Thickness Variation ◽  
Glacial Isostatic Adjustment ◽  
Lithospheric Thickness ◽  
Isostatic Adjustment ◽  
Mantle Viscosity ◽  
Open Questions

<p>Holocene relative sea-level (RSL) records from regions distal from ice sheets (far-field) are commonly characterized by a mid-Holocene highstand, when RSL reached higher than present levels. The magnitude and timing of the mid-Holocene highstand varies spatially due to hydro-isostatic processes including ocean syphoning and continental levering. While there are open questions regarding the timing, magnitude and source of ice-equivalent sea level in the middle to late Holocene.</p><p>Here, we compare Glacial Isostatic Adjustment (GIA) model predictions to a standardized database of sea-level index points (SLIPs) from Southeast Asia where we have near-complete Holocene records. The database has more than 130 SLIPs that span the time period from ~9.5 ka BP to present. We investigate the sensitivity of mid-Holocene RSL predictions to GIA parameters, including the lateral lithospheric thickness variation, mantle viscosity (both 1D and 3D), and deglaciation history from different ice sheets (e.g., Laurentide, Fennoscandia, Antarctica).</p><p>We compute gravitationally self-consistent RSL histories for the GIA model with time dependent coastlines and rotational feedback using the Coupled Laplace-Finite Element Method. The preliminary results show that the timing of the highstand is mainly controlled by the deglaciation history (ice-equivalent sea level), while the magnitude is dominated by Earth parameters (e.g., lithospheric thickness, mantle viscosity). We further investigate whether there is meltwater input during middle to late Holocene and whether the RSL records from Southeast Asia can reveal the meltwater source, like Antarctica.</p>

scholarly journals Joint inversion estimate of regional glacial isostatic adjustment in Antarctica considering a lateral varying Earth structure (ESA STSE Project REGINA)

2017 ◽  
Vol 211 (3) ◽  
pp. 1534-1553 ◽  
Author(s):  
Ingo Sasgen ◽  
Alba Martín-Español ◽  
Alexander Horvath ◽  
Volker Klemann ◽  
Elizabeth J Petrie ◽  
...  
Keyword(s):  
Joint Inversion ◽  
Earth Structure ◽  
Glacial Isostatic Adjustment ◽  
Isostatic Adjustment

Glacial isostatic adjustment and mantle viscosity

1988 ◽  
Vol 93 (B6) ◽  
pp. 6397 ◽  
Author(s):  
Charles B. Officer ◽  
Walter S. Newman ◽  
John M. Sullivan ◽  
Daniel R. Lynch
Keyword(s):  
Glacial Isostatic Adjustment ◽  
Isostatic Adjustment ◽  
Mantle Viscosity

scholarly journals Altimetry, gravimetry, GPS and viscoelastic modelling data for the joint inversion for glacial isostatic adjustment in Antarctica (ESA STSE Project REGINA)

2017 ◽  
Author(s):  
Ingo Sasgen ◽  
Alba Martín-Español ◽  
Alexander Horvath ◽  
Volker Klemann ◽  
Elizabeth J. Petrie ◽  
...  
Keyword(s):  
Solid Earth ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Data Sets ◽  
Glacial Isostatic Adjustment ◽  
Response Functions ◽  
Forward Modelling ◽  
Satellite Gravimetry ◽  
Isostatic Adjustment ◽  
The Antarctic

Abstract. A major uncertainty in determining the mass balance of the Antarctic ice sheet from measurements of satellite gravimetry, and to a lesser extent satellite altimetry, is the poorly known correction for the ongoing deformation of the solid Earth caused by glacial isostatic adjustment (GIA). In the past decade, much progress has been made in consistently modelling the ice sheet and solid Earth interactions; however, forward-modelling solutions of GIA in Antarctica remain uncertain due to the sparsity of constraints on the ice sheet evolution, as well as the Earth's rheological properties. An alternative approach towards estimating GIA is the joint inversion of multiple satellite data – namely, satellite gravimetry, satellite altimetry and GPS, which reflect, with different sensitivities, trends of recent glacial changes and GIA. Crucial to the success of this approach is the accuracy of the space-geodetic data sets. Here, we present reprocessed rates of surface-ice elevation change (Envisat/ICESat; 2003–2009), gravity field change (GRACE; 2003–2009) and bedrock uplift (GPS; 1995–2013.7). The data analysis is complemented by the forward-modelling of viscoelastic response functions to disc load forcing, allowing us to relate GIA-induced surface displacements with gravity changes for different rheological parameters of the solid Earth. The data and modelling results presented here are available in the Pangea archive; https://doi.pangaea.de/10.1594/PANGAEA.875745. The data sets are the input streams for the joint inversion estimate of present-day ice-mass change and GIA, focusing on Antarctica. However, the methods, code and data provided in this paper are applicable to solve other problems, such as volume balances of the Antarctic ice sheet, or to other geographical regions, in the case of the viscoelastic response functions. This paper presents the first of two contributions summarizing the work carried out within a European Space Agency funded study, REGINA.

3D glacial-isostatic adjustment models using geodynamically constrained Earth structures

2021 ◽  
Author(s):  
Meike Bagge ◽  
Volker Klemann ◽  
Bernhard Steinberger ◽  
Milena Latinović ◽  
Maik Thomas
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Glacial Isostatic Adjustment ◽  
Level Change ◽  
Isostatic Adjustment ◽  
Mantle Viscosity ◽  
The Earth ◽  
Earth Structures

<p>The interaction between ice sheets and the solid Earth plays an important role for ice-sheet stability and sea-level change and hence for global climate models. Glacial-isostatic adjustment (GIA) models enable simulation of the solid Earth response due to variations in ice-sheet and ocean loading and prediction of the relative sea-level change. Because the viscoelastic response of the solid Earth depends on both ice-sheet distribution and the Earth’s rheology, independent constraints for the Earth structure in GIA models are beneficial. Seismic tomography models facilitate insights into the Earth’s interior, revealing lateral variability of the mantle viscosity that allows studying its relevance in GIA modeling. Especially, in regions of low mantle viscosity, the predicted surface deformations generated with such 3D GIA models differ considerably from those generated by traditional GIA models with radially symmetric structures. But also, the conversion from seismic velocity variations to viscosity is affected by a set of uncertainties. Here, we apply geodynamically constrained 3D Earth structures. We analyze the impact of conversion parameters (reduction factor in Arrhenius law and radial viscosity profile) on relative sea-level predictions. Furthermore, we focus on exemplary low-viscosity regions like the Cascadian subduction zone and southern Patagonia, which coincide with significant ice-mass changes.</p>

Using magnetotelluric and seismic geophysical observations to infer viscosity for Glacial Isostatic Adjustment calculations

2020 ◽  
Author(s):  
Florence Ramirez ◽  
Kate Selway ◽  
Clinton Conrad
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Water Content ◽  
Seismic Attenuation ◽  
Conversion Process ◽  
Glacial Isostatic Adjustment ◽  
Partial Melt ◽  
Isostatic Adjustment ◽  
Mantle Viscosity ◽  
The Impact

<p>A physical property that is important for understanding the geodynamics of Earth’s lithosphere and asthenosphere is the effective viscosity <em>η<sub>eff</sub></em> (the ratio of stress and strain rate). This is particularly important for accurate Glacial Isostatic Adjustment (GIA) calculations, which are increasingly crucial for estimating ice loss and sea level rise from the Greenland and Antarctic ice sheets. Mantle viscosity cannot be measured directly, but can be inferred from strain rate, for example as observed by ground uplift following deglaciation or a seismic event. Empirically, mantle strain rate is mainly controlled by stress, temperature, grain size, and composition (water content and partial melt). The influence of these controlling parameters can be inferred from geophysical observations such as seismic and magnetotelluric (MT) measurements, which are useful for imaging the subsurface of the Earth but do not directly constrain viscosity. These observations can be used to improve constraints on viscosity using a three-step conversion process: (1) constrain temperature from MT, seismic, and other data; (2) constrain compositional structure from MT and seismic data (water content of nominally anhydrous minerals from MT, partial melt content from MT and seismics); and finally, (3) convert the calculated thermal and compositional structures into a constrained viscosity structure. In each conversion process, we can assess and quantify the involved uncertainties. Furthermore, we determine the dominant deformation regime in order to accurately interpret the sensitivity of viscosity to its controlling parameters. For instance, water content strongly affects viscosity for the dislocation-accommodated grain-boundary sliding (dis-GBS) and dislocation creep regimes, while diffusion creep and dis-GBS are highly sensitive to grain size. Stress and grain size are important parameters for determining where these critical transitions may occur. Although neither MT nor seismic velocity observations place strong constraints on grain size, information about seismic attenuation or tectonic history can potentially provide information about grain–size. Overall, we find that seismic and MT observations together can significantly improve estimates of mantle viscosity, and in particular can place useful constraints on the amplitude of regional variations in mantle viscosity. Such constraints will be particularly useful for studies to estimate the impact of such variations on GIA processes.</p>

scholarly journals Lithosphere and upper-mantle structure of the southern Baltic Sea estimated from modelling relative sea-level data with glacial isostatic adjustment

2013 ◽  
Vol 5 (2) ◽  
pp. 2483-2507
Author(s):  
H. Steffen ◽  
G. Kaufmann ◽  
R. Lampe
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Upper Mantle ◽  
Glacial Isostatic Adjustment ◽  
Relative Sea Level ◽  
Southern Baltic Sea ◽  
Lithospheric Thickness ◽  
Isostatic Adjustment ◽  
Mantle Viscosity ◽  
Ice Model

Abstract. During the last glacial maximum, a large ice sheet covered Scandinavia, and the Earth's surface was depressed by several 100 m. Beyond the limit of this Fennoscandian ice sheet, mass redistribution in the upper mantle led to the development of peripheral bulges around the glaciated region. These once uplifted areas subside since the begin of deglaciation due to the viscoelastic behavior of the mantle. Parts of this subsiding region are located in northern central Europe in the coastal parts of Denmark, Germany and Poland. We analyze relative sea-level (RSL) data of these regions to determine the lithospheric thickness and radial mantle viscosity structure for distinct regional RSL subsets. We load a one-dimensional Maxwell-viscoelastic earth model with a global ice-load history model of the last glaciation. We test two commonly used ice histories, RSES from the Australian National University and Ice-5G from the University of Toronto. Our results indicate that the lithospheric thickness varies, depending on the ice model used, between 60 and 160 km. The lowest values are found in the Oslo Graben area and the western German Baltic Sea coast. In between, thickness increases by at least 30 km tracing the Fyn High. In Poland, lithospheric thickness values up to 160 km are reached. However, the latter values are not well constrained due to a low number of RSL data from the Polish area. Upper-mantle viscosity is found to bracket [2–7] × 1020 Pa s when using Ice-5G. Employing RSES much higher values of 2 × 1021 Pa s yield for the southern Baltic Sea, which suggests a revision of this ice-model version. We confirm that the lower-mantle viscosity in Fennoscandia can only be poorly resolved. The lithospheric structure inferred partly supports structural features of regional and global lithosphere models based on thermal or seismological data. While there is agreement in eastern Europe and southwest Sweden, the structure in an area from south of Norway to northern Germany shows large discrepancies for two of the tested models. It thus remains challenging to sufficiently determine the Fyn High as seen with seismics with the help of glacial isostatic adjustment modelling.

scholarly journals The glacial isostatic adjustment signal at present day in northern Europe and the British Isles estimated from geodetic observations and geophysical models

Solid Earth ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 777-795 ◽  
Author(s):  
Karen M. Simon ◽  
Riccardo E. M. Riva ◽  
Marcel Kleinherenbrink ◽  
Thomas Frederikse
Keyword(s):  
Mass Loss ◽  
Barents Sea ◽  
Joint Inversion ◽  
Vertical Motion ◽  
Ice Age ◽  
Northern Europe ◽  
Glacial Isostatic Adjustment ◽  
British Isles ◽  
Isostatic Adjustment ◽  
Vertical Land Motion

Abstract. The glacial isostatic adjustment (GIA) signal at present day is constrained via the joint inversion of geodetic observations and GIA models for a region encompassing northern Europe, the British Isles, and the Barents Sea. The constraining data are Global Positioning System (GPS) vertical crustal velocities and GRACE (Gravity Recovery and Climate Experiment) gravity data. When the data are inverted with a set of GIA models, the best-fit model for the vertical motion signal has a χ2 value of approximately 1 and a maximum a posteriori uncertainty of 0.3–0.4 mm yr−1. An elastic correction is applied to the vertical land motion rates that accounts for present-day changes to terrestrial hydrology as well as recent mass changes of ice sheets and glaciered regions. Throughout the study area, mass losses from Greenland dominate the elastic vertical signal and combine to give an elastic correction of up to +0.5 mm yr−1 in central Scandinavia. Neglecting to use an elastic correction may thus introduce a small but persistent bias in model predictions of GIA vertical motion even in central Scandinavia where vertical motion is dominated by GIA due to past glaciations. The predicted gravity signal is generally less well-constrained than the vertical signal, in part due to uncertainties associated with the correction for contemporary ice mass loss in Svalbard and the Russian Arctic. The GRACE-derived gravity trend is corrected for present-day ice mass loss using estimates derived from the ICESat and CryoSat missions, although a difference in magnitude between GRACE-inferred and altimetry-inferred regional mass loss rates suggests the possibility of a non-negligible GIA response here either from millennial-scale or Little Ice Age GIA.

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