scholarly journals Glacial Isostatic Adjustment modelling: historical perspectives, recent advances, and future directions

2018 ◽  
Author(s):  
Pippa L. Whitehouse
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Measurement Techniques ◽  
Ice Sheets ◽  
Order Effects ◽  
System Modelling ◽  
Glacial Isostatic Adjustment ◽  
Future Directions ◽  
Historical Perspectives ◽  
Isostatic Adjustment

Abstract. Glacial Isostatic Adjustment (GIA) describes the response of the solid Earth, the gravitational field, and consequently the oceans to the growth and decay of the global ice sheets. It is a process that takes place relatively rapidly, triggering 100 m-scale changes in sea level and solid Earth deformation over just a few tens of thousands of years. Indeed, the first-order effects of GIA could already be quantified several hundred years ago without reliance on precise measurement techniques and scientists have been developing a unifying theory for the observations for over 200 years. Progress towards this goal required a number of significant breakthroughs to be made, including the recognition that ice sheets were once more extensive, the solid Earth changes shape over time, and gravity plays a central role in determining the pattern of sea-level change. This article describes in detail the historical development of the field of GIA and an overview of the processes involved. Significant recent progress has been made as concepts associated with GIA have begun to be incorporated into parallel fields of research; these advances are discussed, along with the role that GIA is likely to play in addressing outstanding research questions within the field of Earth system modelling.

scholarly journals Glacial isostatic adjustment modelling: historical perspectives, recent advances, and future directions

2018 ◽  
Vol 6 (2) ◽  
pp. 401-429 ◽  
Author(s):  
Pippa L. Whitehouse
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Land Surface ◽  
Measurement Techniques ◽  
Ice Sheets ◽  
Order Effects ◽  
System Modelling ◽  
Glacial Isostatic Adjustment ◽  
Historical Perspectives ◽  
Isostatic Adjustment

Abstract. Glacial isostatic adjustment (GIA) describes the response of the solid Earth, the gravitational field, and the oceans to the growth and decay of the global ice sheets. A commonly studied component of GIA is “postglacial rebound”, which specifically relates to uplift of the land surface following ice melt. GIA is a relatively rapid process, triggering 100 m scale changes in sea level and solid Earth deformation over just a few tens of thousands of years. Indeed, the first-order effects of GIA could already be quantified several hundred years ago without reliance on precise measurement techniques and scientists have been developing a unifying theory for the observations for over 200 years. Progress towards this goal required a number of significant breakthroughs to be made, including the recognition that ice sheets were once more extensive, the solid Earth changes shape over time, and gravity plays a central role in determining the pattern of sea-level change. This article describes the historical development of the field of GIA and provides an overview of the processes involved. Significant recent progress has been made as concepts associated with GIA have begun to be incorporated into parallel fields of research; these advances are discussed, along with the role that GIA is likely to play in addressing outstanding research questions within the field of Earth system 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>

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>

Dynamic Topography Change of the Eastern United States Since 3 Million Years Ago

Science ◽  
2013 ◽  
Vol 340 (6140) ◽  
pp. 1560-1563 ◽  
Author(s):  
David B. Rowley ◽  
Alessandro M. Forte ◽  
Robert Moucha ◽  
Jerry X. Mitrovica ◽  
Nathan A. Simmons ◽  
...  
Keyword(s):  
Sea Level ◽  
Coastal Plain ◽  
Mantle Convection ◽  
Sedimentary Rocks ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Eastern United States ◽  
Dynamic Topography ◽  
Isostatic Adjustment ◽  
Global Sea Level

Sedimentary rocks from Virginia through Florida record marine flooding during the mid-Pliocene. Several wave-cut scarps that at the time of deposition would have been horizontal are now draped over a warped surface with a maximum variation of 60 meters. We modeled dynamic topography by using mantle convection simulations that predict the amplitude and broad spatial distribution of this distortion. The results imply that dynamic topography and, to a lesser extent, glacial isostatic adjustment account for the current architecture of the coastal plain and proximal shelf. This confounds attempts to use regional stratigraphic relations as references for longer-term sea-level determinations. Inferences of Pliocene global sea-level heights or stability of Antarctic ice sheets therefore cannot be deciphered in the absence of an appropriate mantle dynamic reference frame.

A Standardized Database of Marine Isotope Stage 5a and 5c Paleo-Shoreline Indicators

2021 ◽  
Author(s):  
Schmitty B. Thompson ◽  
Jessica R. Creveling
Keyword(s):  
North America ◽  
Sea Level ◽  
Atlantic Coast ◽  
Ice Sheets ◽  
Climate Projections ◽  
Glacial Isostatic Adjustment ◽  
Last Interglacial ◽  
Comprehensive Overview ◽  
Isostatic Adjustment ◽  
The Caribbean

<p>Reconstructions of global mean sea level (GMSL) through interstadials such as Marine Isotope Stages (MIS) 5a and 5c provide important constraints on the rates of growth and collapse of major ice sheets during warm periods analogous to future climate projections. These reconstructions rely upon precisely dated geomorphic and sedimentological indicators for past sea level whose present elevations are complicated by tectonics and glacial isostatic adjustment (GIA). Compilations of MIS 5a and 5c paleo-sea level indicators that covering a wide geographic range can be used to minimize misfit with glacial isostatic adjustment models and thereby quantify and refine the convolved contribution of GMSL to the present elevation of paleo-shoreline indicators. Here we present a global compilation of previously published Marine Isotope Stages 5a and 5c local sea level indicators from 39 sites covering three main regions: the Pacific coast of North America, the Atlantic coast of North America and the Caribbean, and far field. We describe the standardized entry of these data into the World Atlas of Last Interglacial Shorelines (WALIS) database. Each entry within the MIS 5a and 5c WALIS database reproduces from the primary literature the indicator elevation, indicative meaning, and geochronology, along with a comprehensive overview of the literature for each site. While MIS 5a and 5c indicators sites are geographically widespread, these data are also patchy and preferentially represent the North American continent and the Caribbean and, hence, regions intermediate and far afield of the contemporaneous ice sheets. While this dataset will support future refinements to MIS 5a and 5c GMSL reconstructions arising from GIA modeling, it also motivates further data collection.</p>

scholarly journals SELEN<sup>4</sup> (SELEN version 4.0): a Fortran program for solving the gravitationally and topographically self-consistent Sea Level Equation in Glacial Isostatic Adjustment modeling

2019 ◽  
Author(s):  
Giorgio Spada ◽  
Daniele Melini
Keyword(s):  
Open Source ◽  
Sea Level ◽  
Late Pleistocene ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Open Source Program ◽  
Isostatic Adjustment ◽  
Source Program ◽  
Supplementary Document ◽  
Self Consistent

Abstract. We present SELEN4 (a SealEveL EquatioN solver), an open-source program written in Fortran 90 that simulates the Glacial Isostatic Adjustment (GIA) process in response to the melting of the late-Pleistocene ice sheets. Using a pseudo-spectral approach complemented by a spatial discretization on an icosahedron-based spherical geodesic grid, SELEN4 solves a generalised Sea Level Equation (SLE) for a spherically symmetric Earth with linear viscoelastic rheology, taking the migration of the shorelines and the rotational feedback on sea level into account. The approach is gravitationally and topographically self-consistent, since it considers the gravitational interactions between the solid Earth, the cryosphere and the oceans, and it accounts for the evolution of the Earth's topography in response to changes in sea level. Program SELEN4 can be employed to study a broad range of geophysical effects of GIA, including past relative sea-level variations induced by the melting of the late-Pleistocene ice sheets, the time-evolution of paleogeography and of the ocean function since the Last Glacial Maximum, the history of the Earth's rotational variations, present-day geodetic signals observed by Global Navigation Satellite Systems and geopotential field variations detected by satellite gravity missions like GRACE (the Gravity Recovery and Climate Experiment). The GIA fingerprints constitute a standard output of SELEN4. Along with the source code, we provide a supplementary document with a full account of the theory, some numerical results obtained from a standard run, and a User guide. Program SELEN was conceived by GS in 2005 as a tool for students eager to learn about GIA. Still, it is the only open-source program for the solution of the SLE available to the community.

scholarly journals A new Holocene sea-level record for Singapore

The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Stephen Chua ◽  
Adam D Switzer ◽  
Tanghua Li ◽  
Huixian Chen ◽  
Margaret Christie ◽  
...  
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Ice Sheets ◽  
Early Holocene ◽  
Glacial Isostatic Adjustment ◽  
Present Level ◽  
Isostatic Adjustment ◽  
Model Predictions ◽  
Regional Processes ◽  
Holocene Sea Level

Relative sea-level (RSL) records from far-field regions distal from ice sheets remain poorly understood, particularly in the early Holocene. Here, we extended the Holocene RSL data from Singapore by producing early Holocene sea-level index points (SLIPs) and limiting dates from a new ~40 m sediment core. We merged new and published RSL data to construct a standardized Singapore RSL database consisting of 88 SLIPs and limiting data. In the early Holocene, RSL rose rapidly from −21.0 to −0.7 m from ~9500 to 7000 cal. yrs. BP. Thereafter, the rate of RSL rise decelerated, reaching a mid-Holocene highstand of 4.0 ± 4.5 m at 5100 cal. yrs. BP, before falling to its present level. There is no evidence of any inflections in RSL when the full uncertainty of SLIPs is considered. When combined with other standardized data from the Malay-Thai Peninsula, our results also show substantial misfits between regional RSL reconstructions and glacial isostatic adjustment (GIA) model predictions in the rate of early Holocene RSL rise, the timing of the mid-Holocene highstand and the nature of late-Holocene RSL fall towards the present. It is presently unknown whether these misfits are caused by regional processes, such as subsidence of the continental shelf, or inaccurate parameters used in the GIA model.

scholarly journals SELEN<sup>4</sup> (SELEN version 4.0): a Fortran program for solving the gravitationally and topographically self-consistent sea-level equation in glacial isostatic adjustment modeling

2019 ◽  
Vol 12 (12) ◽  
pp. 5055-5075 ◽  
Author(s):  
Giorgio Spada ◽  
Daniele Melini
Keyword(s):  
Sea Level ◽  
Late Pleistocene ◽  
Ice Sheets ◽  
Global Navigation Satellite Systems ◽  
Glacial Isostatic Adjustment ◽  
Satellite Gravity ◽  
Full Account ◽  
Isostatic Adjustment ◽  
Supplementary Document ◽  
Self Consistent

Abstract. We present SELEN4 (SealEveL EquatioN solver), an open-source program written in Fortran 90 that simulates the glacial isostatic adjustment (GIA) process in response to the melting of the Late Pleistocene ice sheets. Using a pseudo-spectral approach complemented by a spatial discretization on an icosahedron-based spherical geodesic grid, SELEN4 solves a generalized sea-level equation (SLE) for a spherically symmetric Earth with linear viscoelastic rheology, taking the migration of the shorelines and the rotational feedback on sea level into account. The approach is gravitationally and topographically self-consistent, since it considers the gravitational interactions between the solid Earth, the cryosphere, and the oceans, and it accounts for the evolution of the Earth's topography in response to changes in sea level. The SELEN4 program can be employed to study a broad range of geophysical effects of GIA, including past relative sea-level variations induced by the melting of the Late Pleistocene ice sheets, the time evolution of paleogeography and of the ocean function since the Last Glacial Maximum, the history of the Earth's rotational variations, present-day geodetic signals observed by Global Navigation Satellite Systems, and gravity field variations detected by satellite gravity missions like GRACE (the Gravity Recovery and Climate Experiment). The “GIA fingerprints” constitute a standard output of SELEN4. Along with the source code, we provide a supplementary document with a full account of the theory, some numerical results obtained from a standard run, and a user guide. Originally, the SELEN program was conceived by Giorgio Spada (GS) in 2005 as a tool for students eager to learn about GIA, and it has been the first SLE solver made available to the community.

Leveraging non-traditional evidence for glacial isostatic adjustment to constrain past ice sheets

2021 ◽  
Author(s):  
Tamara Pico
Keyword(s):  
Sea Level ◽  
Current Knowledge ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ice Age ◽  
Small Scale ◽  
Glacial Isostatic Adjustment ◽  
Continental Scale ◽  
Isostatic Adjustment ◽  
Ice Stream

&lt;p&gt;Although understanding the response of ice sheets to a changing climate is a pressing issue of this century, our current knowledge of past ice-sheet changes remains limited by data sparsity. I explore approaches that leverage non-traditional datasets to constrain past ice sheet and sea-level change over the last glacial cycle. For example, I consider the potential to use past landscapes to infer crustal deformation induced by ice sheet loading. Over the ice-age, glacial isostatic adjustment produces rates of uplift comparable to some of the fastest tectonic uplift rates (~10 mm/yr) in regions hundreds of kilometers away from the maximum ice sheet extent. Additionally, I show it is possible to gain insight into longer-term continental scale ice sheet deglacial histories using small-scale ice stream dynamics. Using records for a rapid retreat of the Amundsen Gulf Ice Stream, located on the northwest Laurentide Ice Sheet, along with observations of the Bering Strait flooding as sea-level indicators, I fingerprint the timing and location of North American saddle deglaciation.&lt;/p&gt;

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