Frequency Dependent Mantle Viscoelasticity via the Complex Viscosity: Cases From Antarctica

Lau, H. C. P.; Austermann, Jacqueline; Holtzman, B. K.; Havlin, C.; Lloyd, A. J.; Book, Cameron; Hopper, Emily

doi:10.1029/2021jb022622

Cited by 24 publications

(27 citation statements)

References 116 publications

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“…Such rheological complexity may also contribute to, or even generate, confined regions with effectively low viscosity, of the sort that we have modeled here. Regardless, the impact of rheological complexity needs more investigation and could help to reconcile models and observations of uplift (Adhikari et al, 2021;Blank et al, 2021;Lau et al, 2021). Bevis et al (2012) found that in most of coastal Greenland the elastic response to contemporary ice mass change matches the historic viscous response or dominates the uplift signal.…”

Section: Factors Affecting Uplift From Contemporary Ice Meltmentioning

confidence: 99%

“…For example, several studies focused on similar locations have resulted in different estimates for mantle viscosity and lithosphere thickness based on historical sea level data and present-day deformation. Lau et al (2021) argued that these different estimates result from different timescales of deformation and that transient, frequency-dependent, rheology may play an important role on GIA timescales. Kang et al (2022) showed that stress-dependent rheology causes temporal variations in upper mantle viscosity due to stress variations during the last deglaciation (ended 8,000 years ago), and that the effects can be rather localized (i.e., affecting load-proximal stresses but not far field stresses).…”

Section: Factors Affecting Uplift From Contemporary Ice Meltmentioning

confidence: 99%

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Solid Earth Uplift Due To Contemporary Ice Melt Above Low‐Viscosity Regions of the Upper Mantle

Weerdesteijn

Conrad

Naliboff

2022

Geophysical Research Letters

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Glacial isostatic adjustment (GIA) is the ongoing response of the solid earth and the geoid to changes in ice and ocean loading, and produces solid earth ground motion that can be measured using GNSS (Global Navigation Satellite Systems). Near areas of past or current ice cover change, it is commonly thought GIA displacements result from a combination of (a) a viscous response to historic ice load changes (i.e., ice age melting), and (b) an elastic response to contemporary ice load changes. Typically, the viscous response occurs over several thousand years, but recent studies have shown regions undergoing rapid viscous uplift on decadal or centennial timescales in response to contemporary ice melt in West Antarctica (Barletta et al., 2018;Nield et al., 2014) and southeast Greenland (Khan et al., 2016). Rapid uplift in these regions is commonly linked to low-viscosities in the upper mantle that accelerate the viscous response to recent melting. In this case, contemporary ice melt generates not only an instantaneous elastic response, but also a viscous response on short timescales. This rapid viscous response is mixed with the other deformation components of GIA (elastic and long-term viscous) that are measured using GNSS, which makes it difficult to distinguish between solid earth deformation due to historical and contemporary ice load changes (Whitehouse, 2018).There are indications that low-viscosity regions of the upper mantle are present beneath both Antarctica and Greenland. Here, we define low-viscosity regions as regions where the viscosity is considerably lower than surrounding mantle material, with a value that can result in deformation on decadal or centennial timescales (e.g., 5 ⋅ 10 19 Pa s or lower), as opposed to thousands of years. Seismic studies in Antarctica show slower velocity anomalies in West compared to East Antarctica (Heeszel et al., 2016;Lloyd et al., 2020), consistent with a colder cratonic region in East Antarctica, and a warmer tectonically active region in West Antarctica, possibly with a mantle plume (Bredow et al., 2021). Lateral variations in mantle temperature, derived from seismic velocity anomalies, suggest lateral variations in mantle rheology (Ivins & Sammis, 1995; van der Wal et al., 2013). Upper

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Section: Factors Affecting Uplift From Contemporary Ice Meltmentioning

confidence: 99%

Section: Factors Affecting Uplift From Contemporary Ice Meltmentioning

confidence: 99%

Solid Earth Uplift Due To Contemporary Ice Melt Above Low‐Viscosity Regions of the Upper Mantle

Weerdesteijn

Conrad

Naliboff

2022

Geophysical Research Letters

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“…It is still an open question as to whether stressdependent viscosity and transient viscosity need to be included in geodynamic models (Ivins et al 2021). In the latter case, is considering short-term and long-term viscosity sufficient or does viscosity need to be considered as a function of loading frequency (Lau et al 2021)? A consistent description of viscosity must consider deformation at the microscopic scale from observations on mantle xenoliths (Chatzaras and Kruckenberg 2021) and laboratory experiments (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…van der Wal et al 2013). In general, viscosity can be seen as dependent on the frequency of loading (Lau et al 2021). What viscosity is representative for which mantle process in Antarctica and how can they be integrated?…”

Section: How Does Lithospheric Thickness Vary Across Antarctica?mentioning

confidence: 99%

An introduction to the geochemistry and geophysics of the Antarctic mantle

Martin

Wal

Boer

2022

Memoirs

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The Antarctic mantle, bounded between the core and the Mohorovičić discontinuity, is one of the most difficult targets of study on Earth because of ice cover and rare outcrop. A multidisciplinary approach is adopted in this volume, using petrology, geochemistry, remote sensed data and geodesy, to characterise the Antarctic mantle. This characterisation has application to rates of glacial isostatic adjustment, heat flow, sea level rise and tectonics. It places the Antarctic mantle domain in a global framework on a scale not attempted before. In this chapter we review the historical development of mantle studies in Antarctica, outline current research directions, introduce the volume chapters and provide a summary and outlook.

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“…These ranges of values reflect typical spatially-averaged estimates for the entirety of Greenland and Antarctica 28 – 31 . Note that this lithosphere thickness is not equivalent to T e ; it instead describes the thickness of an idealised elastic layer above the viscoelastic mantle appropriate for ice age timescales 32 . For the above range of mantle viscosities, the timescale required for the residual disequilibrium to decay by a factor of 1/5 e from its post-LGM peak value and thereby reach approximate steady state varies from 30 to 70 kyr.…”

Section: Methodsmentioning

confidence: 99%

Total isostatic response to the complete unloading of the Greenland and Antarctic Ice Sheets

Paxman

Austermann

Hollyday

2022

Sci Rep

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The land surface beneath the Greenland and Antarctic Ice Sheets is isostatically suppressed by the mass of the overlying ice. Accurate computation of the land elevation in the absence of ice is important when considering, for example, regional geodynamics, geomorphology, and ice sheet behaviour. Here, we use contemporary compilations of ice thickness and lithospheric effective elastic thickness to calculate the fully re-equilibrated isostatic response of the solid Earth to the complete removal of the Greenland and Antarctic Ice Sheets. We use an elastic plate flexure model to compute the isostatic response to the unloading of the modern ice sheet loads, and a self-gravitating viscoelastic Earth model to make an adjustment for the remaining isostatic disequilibrium driven by ice mass loss since the Last Glacial Maximum. Feedbacks arising from water loading in areas situated below sea level after ice sheet removal are also taken into account. In addition, we quantify the uncertainties in the total isostatic response associated with a range of elastic and viscoelastic Earth properties. We find that the maximum change in bed elevation following full re-equilibration occurs over the centre of the landmasses and is +783 m in Greenland and +936 m in Antarctica. By contrast, areas around the ice margins experience up to 123 m of lowering due to a combination of sea level rise, peripheral bulge collapse, and water loading. The computed isostatic response fields are openly accessible and have a number of applications for studying regional geodynamics, landscape evolution, cryosphere dynamics, and relative sea level change.

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Frequency Dependent Mantle Viscoelasticity via the Complex Viscosity: Cases From Antarctica

Cited by 24 publications

References 116 publications

Solid Earth Uplift Due To Contemporary Ice Melt Above Low‐Viscosity Regions of the Upper Mantle

Solid Earth Uplift Due To Contemporary Ice Melt Above Low‐Viscosity Regions of the Upper Mantle

An introduction to the geochemistry and geophysics of the Antarctic mantle

Total isostatic response to the complete unloading of the Greenland and Antarctic Ice Sheets

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