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>

scholarly journals Refining Estimates of Polar Ice Volumes during the MIS11 Interglacial Using Sea Level Records from South Africa

2014 ◽  
Vol 27 (23) ◽  
pp. 8740-8746 ◽  
Author(s):  
Florence Chen ◽  
Sarah Friedman ◽  
Charles G. Gertler ◽  
James Looney ◽  
Nizhoni O’Connell ◽  
...  
Keyword(s):  
South Africa ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Polar Ice ◽  
Level Change ◽  
Isostatic Adjustment ◽  
West Antarctic ◽  
Numerical Predictions

Abstract Peak eustatic sea level (ESL), or minimum ice volume, during the protracted marine isotope stage 11 (MIS11) interglacial at ~420 ka remains a matter of contention. A recent study of high-stand markers of MIS11 age from the tectonically stable southern coast of South Africa estimated a peak ESL of 13 m. The present study refines this estimate by taking into account both the uncertainty in the correction for glacial isostatic adjustment (GIA) and the geographic variability of sea level change following polar ice sheet collapse. In regard to the latter, the authors demonstrate, using gravitationally self-consistent numerical predictions of postglacial sea level change, that rapid melting from any of the three major polar ice sheets (West Antarctic, Greenland, or East Antarctic) will lead to a local sea level rise in southern South Africa that is 15%–20% higher than the eustatic sea level rise associated with the ice sheet collapse. Taking this amplification and a range of possible GIA corrections into account and assuming that the tectonic correction applied in the earlier study is correct, the authors revise downward the estimate of peak ESL during MIS11 to 8–11.5 m.

Observations of postglacial uplift at Churchill, Manitoba

1992 ◽  
Vol 29 (11) ◽  
pp. 2418-2425 ◽  
Author(s):  
A. Mark Tushingham
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Glacial Isostatic Adjustment ◽  
Tide Gauge Record ◽  
Isostatic Adjustment ◽  
Absolute Gravimetry ◽  
The Earth ◽  
Level Data

Churchill, Manitoba, is located near the centre of postglacial uplift caused by the Earth's recovery from the melting of the Laurentide Ice Sheet. The value of present-day uplift at Churchill has important implications in the study of postglacial uplift in that it can aid in constraining the thickness of the ice sheet and the rheology of the Earth. The tide-gauge record at Churchill since 1940 is examined, along with nearby Holocene relative sea-level data, geodetic measurements, and recent absolute gravimetry measurements, and a present-day rate of uplift of 8–9 mm/a is estimated. Glacial isostatic adjustment models yield similar estimates for the rate of uplift at Churchill. The effects of the tide-gauge record of the diversion of the Churchill River during the mid-1970's are discussed.

The influence of the solid Earth on the contribution of marine sections of the Antarctic ice sheet to future sea level change

2021 ◽  
Author(s):  
Maryam Yousefi ◽  
Jeannette Wang ◽  
Linda Pan ◽  
Natalya Gomez ◽  
Konstantin Latychev ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Solid Earth ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Earth Structure ◽  
Level Change ◽  
Grounding Line ◽  
Level Model ◽  
The Antarctic

<p>The future retreat of marine-based sectors of the Antarctic Ice Sheet (AIS) and its consequent global mean sea level (GMSL) rise is driven by various climatic and non-climatic feedbacks between ice, ocean, atmosphere, and solid Earth. The primary mode of ice loss in marine sectors of the AIS is dynamic flow of ice across the grounding line into the ocean. The flux of ice across the grounding line is strongly sensitive to the thickness of ice there, which is in turn proportional to the water depth (sea level) such that sea level rise enhances ice loss and grounding line retreat while sea level fall acts to slow or stop migration of the grounding line. In response to the unloading from removal of ice mass, the underlying bedrock deforms isostatically leading to lower local sea surface which promotes stabilization of the grounding line. In addition to its effect on AIS evolution, solid Earth deformation also alters the shape and size of the ocean basin areas that are exposed as marine areas of ice retreat and influences the amount of meltwater that leaves Antarctica and contributes to global sea-level rise. The solid Earth deformational response to surface loading changes, in terms of both magnitude and timescales, depends on Earth rheology. Seismic tomography models indicate that the interior structure of the Earth is highly variable over the Antarctica with anomalously low shallow mantle viscosities across the western section of the AIS. An improved projection of the contribution from AIS to sea level change requires a consideration of this complexity in Earth structure. Here we adopt a state-of-the-art seismic velocity model to build a high-resolution 3D viscoelastic structure model beneath Antarctica. We incorporate this structure into a high spatiotemporal resolution sea-level model to simulate the influence of solid Earth deformation on contributions of the AIS evolution to future sea-level change. Our sea-level model is coupled with the dynamics of PSU ice sheet model and our calculations are based on a range of future climate forcings. We show that the influence of applying a spatially variable Earth structure is significant, particularly in the regions of West Antarctica where upper mantle viscosities are lower and the elastic lithosphere is thinned.</p>

A revised sea level budget equation to accurately represent physical processes driving sea level rise

2020 ◽  
Author(s):  
Bramha Dutt Vishwakarma ◽  
Sam Royston ◽  
Ricardo E. M. Riva ◽  
Richard M. Westaway ◽  
Jonathan L. Bamber
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Sea Level Change ◽  
Ocean Bottom ◽  
Physical Processes ◽  
Level Change ◽  
Ocean Mass ◽  
The Earth ◽  
Regional Sea Level ◽  
Global Mean

<p>The sea level budget (SLB) equates changes in sea surface height (SSH) to the sum of various geo-physical processes that contribute to sea level change. Currently, it is a common practice to explain a change in SSH as a sum of ocean mass and steric change, assuming that solid-Earth motion is corrected for and completely explained by secular visco-elastic relaxation of mantle, due to the process of glacial isostatic adjustment. Yet, since the Solid Earth also responds elastically to changes in present day mass load near the surface of the Earth, we can expect the ocean bottom to respond to ongoing ocean mass changes. This elastic ocean bottom deformation (OBD) has been ignored until very recently because the contribution of ocean mass to sea level rise was thought to be smaller than the steric contribution and the resulting OBD was within observation system uncertainties. However, ocean mass change has increased rapidly in the last 2 decades. Therefore, OBD is no longer negligible and recent studies have shown that its magnitude is similar to that of the deep steric sea level contribution: a global mean of about 0.1 mm/yr but regional changes at some places can be more than 10 times the global mean. Although now an important part of the SLB, especially for regional sea level, OBD is considered by only a few budget studies and they treat it as a spatially uniform correction. This is due to lack of a mathematical framework that defines the contribution of OBD to the SLB. Here, we use a mass-volume framework to derive, for the first time, a SLB equation that partitions SSH change into its component parts accurately and it includes OBD as a physical response of the Earth system. This updated SLB equation is important for various disciplines of Earth Sciences that use the SLB equation: as a constraint to assess the quality of observational time-series; as a means to quantify the importance of each component of sea level change; and, to adequately include all processes in global and regional sea level projections. We recommend using the updated SLB equation for sea level budget studies. We also revisit the contemporary SLB with the updated SLB equation using satellite altimetry data, GRACE data, and ARGO data.</p>

scholarly journals The contribution of glacial isostatic adjustment to projections of sea‐level change along the Atlantic and Gulf coasts of North America

2016 ◽  
Vol 4 (10) ◽  
pp. 440-464 ◽  
Author(s):  
Ryan Love ◽  
Glenn A. Milne ◽  
Lev Tarasov ◽  
Simon E. Engelhart ◽  
Marc P. Hijma ◽  
...  
Keyword(s):  
North America ◽  
Sea Level ◽  
Sea Level Change ◽  
Glacial Isostatic Adjustment ◽  
Level Change ◽  
Isostatic Adjustment
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