Glacial-isostatic Adjustment and the Viscosity Structure Underlying the Vatnajökull Ice Cap, Iceland

Fleming, Kevin; Martinec, Zdenĕk; Wolf, Detlef

doi:10.1007/978-3-7643-8417-3_8

Cited by 13 publications

(29 citation statements)

References 57 publications

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“…Assuming water is the only variable a↵ecting the rheology in addition to pressure and temperature, minimum viscosities < 10 19 Pa s as inferred for example for the Western United States (Bills et al, 2007) or Iceland (Fleming et al, 2007) require water contents of > 300 ppm H/Si at a stress of 0.3…”

Section: Application To the Upper Mantlementioning

confidence: 99%

Titanium-hydroxyl defect-controlled rheology of the Earth's upper mantle

Faul

Cline

David

et al. 2016

Earth and Planetary Science Letters

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Experiments were conducted with hydrous olivine to investigate the defect responsible for the influence of water (hydrogen structurally incorporated as hydroxyl) on the olivine rheology. Solution-gelation derived Fo 90 olivine doped with nominally 0.04-0.1 wt.% TiO 2 was first hot-pressed and then deformed in platinum capsules at 300 MPa confining pressure and temperatures from 1200-1350 C. The water content was not bu↵ered so that deformation occurred at water-undersaturated conditions. Due to the enhanced grain growth under hydrous conditions, the samples were at least a factor of three more coarse-grained than their dry counterparts and deformed in powerlaw creep at di↵erential stresses as low as a few tens of MPa. Since all experiments were conducted at the same confining pressure, the essentially linear relationship between strain rate and water content was for the first time determined independently of an activation volume. Infrared spectra are dominated by absorption bands at 3572 and 3525 cm 1. These bands also predominate in

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Section: Application To the Upper Mantlementioning

confidence: 99%

Titanium-hydroxyl defect-controlled rheology of the Earth's upper mantle

Faul

Cline

David

et al. 2016

Earth and Planetary Science Letters

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“…Rheological structure of Iceland has been determined by seismology, and by magnetotelluric and GPS surveys that together have revealed a layered structure of the lithosphere [64]. First, there is about 4 km thick brittle and laterally variable upper crust underlain by about 8 km thick elastic lower crust, and then another about 8 km thick ductile and laterally more uniform layer [22,64]. The asthenosphere below Iceland is about 200 km thick with relatively low viscosity that enables it to flow at high velocities (e.g.…”

Section: Lithospheric and Asthenospheric Properties Below Icelandmentioning

confidence: 99%

Collapse of the Icelandic ice sheet controlled by sea-level rise?

Norðdahl

Inǵólfsson

2015

Arktos

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The deglaciation of the Late Weichselian Icelandic ice sheet was extremely rapid, and marked by a collapse of its marine-based sections between 15.0 and 14.7 ka BP. We present a conceptual two-dimensional glacio-isostatic equilibrium model that describes the effect of simultaneous glacio-isostatic responses to changes in glacier load on the crust and relative eustatic sea level changes during the deglaciation of the Icelandic ice sheet. The deglaciation was characterized by three main steps: (1) slow deglaciation of the outer shelf, progressing between about 18.6-15.0 ka BP, mainly driven by sea-level rise and grounding line retreat on a retrograde slope; (2) an extremely rapid retreat from the shelf areas between 15.0 and 14.7 ka BP, mainly driven by rapid sea-level rise and largescale calving; (3) a slower retreat driven by North Atlantic warming once the ice sheet was inside the coast, between 14.7 and 13.8 ka BP. The very rapid deglaciation of the Iceland shelf areas between 15.0 and 14.7 ka BP does not confirm with linear response to warming, but rather describes a non-linear response, where the ice sheet experiences an abrupt collapse once a threshold defined by relative eustatic sea-level rise is crossed. We propose that rapid eustatic sea-level rise that peaked during Mwp-1A being coeval with the collapse of the marine-based part of the Icelandic ice sheet suggests a causal relationship between the two events.

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“…Unfortunately, we do not have sufficient observational data on the glaciers to constrain an ice model with time‐varying deglaciation rates. We do not model the ice history prior to 1890 since it is less well constrained than the more recent evolution, and the effect of the earlier ice history on present‐day displacement rates is small [ Árnadóttir et al , ; Fleming et al , ]. This is mainly due to the volume of the glaciers being relatively constant between the years 1750 and 1890 [ Thórarinsson , ; Björnsson , ] and the low viscosity of the Icelandic mantle.…”

Section: Modeling Gia Pressure Changes In the Mantlementioning

confidence: 99%

“…Present‐day GIA in Iceland has been studied and modeled by several authors using measurements of tilt rates, GPS, gravity, and, more recently, interferometric synthetic aperture radar (InSAR) [e.g., Sigmundsson and Einarsson , ; Fleming et al , ; Pagli et al , ; Jacoby et al , ; Árnadóttir et al , ; Schmidt et al , ; Auriac et al , ]. Most of the earlier studies assumed axisymmetric models, considering only the deglaciation of Vatnajökull, and used regional observations to constrain the modeling.…”

Section: Introductionmentioning

confidence: 99%

Effects of present‐day deglaciation in Iceland on mantle melt production rates

et al. 2013

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[1] Ongoing deglaciation in Iceland not only causes uplift at the surface but also increases magma production at depth due to decompression of the mantle. Here we study glacially induced decompression melting using 3-D models of glacial isostatic adjustment in Iceland since 1890. We find that the mean glacially induced pressure rate of change in the mantle increases melt production rates by 100-135%, or an additional 0.21-0.23 km 3 of magma per year beneath Iceland. Approximately 50% of this melt is produced underneath central Iceland. The greatest volumetric increase is found directly beneath Iceland's largest ice cap, Vatnajökull, colocated with the most productive volcanoes. Our models of the effect of deglaciation on mantle melting predict a significantly larger volumetric response than previous models which only considered the effect of deglaciation of Vatnajökull, and only mantle melting directly below Vatnajökull. Although the ongoing deglaciation significantly increases the melt production rate, the increase in melt supply rate at the base of the lithosphere is delayed and depends on the melt ascent velocity through the mantle. Assuming that 25% of the melt reaches the surface, the upper limit on our deglaciation-induced melt estimates for central Iceland would be equivalent to an eruption the size of the 2010 Eyjafjallajökull summit eruption every seventh year.

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Glacial-isostatic Adjustment and the Viscosity Structure Underlying the Vatnajökull Ice Cap, Iceland

Cited by 13 publications

References 57 publications

Titanium-hydroxyl defect-controlled rheology of the Earth's upper mantle

Titanium-hydroxyl defect-controlled rheology of the Earth's upper mantle

Collapse of the Icelandic ice sheet controlled by sea-level rise?

Effects of present‐day deglaciation in Iceland on mantle melt production rates

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