A review of ice rheology for ice sheet modelling

Budd, W. F.; Jacka, T. H.

doi:10.1016/0165-232x(89)90014-1

Cited by 441 publications

(527 citation statements)

References 86 publications

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“…This result has broad support from laboratory and field observations, especially at high stresses (er >~ 1 bar) (Weertman, 1973;Hobbs, 1974;Budd and Jacka, 1989); results at lower stresses (a <~ 1 bar) are equivocal as to whether n = 3 or n < 3 (including n = 1), probably because of the great difficulty in conducting such tests (see Weertman, 1973;Budd and J acka, 1989). …”

Section: {4}mentioning

confidence: 91%

“…that delineate the boundaries of some or all of these different regimes have been presented, e.g. by Hooke and Hudleston (1980), Alley (1988) and Budd and Jacka (1989). These may provide useful guidelines, but the inadequacy of the data base and the complex interrelationships of the control parameters must be remembered at all times.…”

Section: Ice-sheet Observationsmentioning

confidence: 99%

“…This is followed downward by a single-maximum, simple-shear region with small grain-size, which often (although not always ) corresponds to WisconsinanjWeichselian ice. If the basal ice is warm, this may be replaced downward by a region of very large grains with a multiple-maximum girdle fabric, which may be caused by annealing associated with fluctuating stresses (Budd and Jacka, 1989). Ice shelves below the firn are characterized by recrystallization girdle fabrics (Fig.…”

Section: Ice-sheet Observationsmentioning

confidence: 99%

“…c-axis fabric development occurs by grain rotation, probably following the Azuma and Higashi (1985) hypothesis as extended by Alley ( 1988). .,., following Budd and Jacka (1989) . Flow-law exponents, fabric controls, grain-growth behavior and microscopic processes are indicated.…”

Section: Synthesesmentioning

confidence: 99%

“…Fabric enhanceDlent froIn Budd and Jacka (1989, fig. 9) Still deeper, the basal shear stress comes to dominate over the normal stresses, so simple shear occurs.…”

Section: Alley: Flow-law Hypotheses For Ice-sheet Modelingmentioning

confidence: 99%

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Flow-law hypotheses for ice-sheet modeling

1992

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ABSTRACT. Ice-flow modeling requires a flow law relating strain rates to stresses in situ, but a flow law cannot be measured directly in ice sheets. Microscopic processes such as dislocation glide and boundary diffusion control both the flow law for ice and the development of physical properties such as grain-size and c-axis fabric. These microscopic processes can be inferred from observations of the physical properties, and the flow law can then be estimated from the microscopic processes.A review of available literature shows that this approach can be imperfectly successful. Interior regions of large ice sheets probably have depth-varying flow-law "constants", with the stress exponent, n, for power-law creep less than 3 in upper regions and equal to 3 only in deep ice; n probably equals 3 through most of the thickness of ice shelves and ice streams.

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Section: {4}mentioning

confidence: 91%

Section: Ice-sheet Observationsmentioning

confidence: 99%

Section: Ice-sheet Observationsmentioning

confidence: 99%

Section: Synthesesmentioning

confidence: 99%

“…Fabric enhanceDlent froIn Budd and Jacka (1989, fig. 9) Still deeper, the basal shear stress comes to dominate over the normal stresses, so simple shear occurs.…”

Section: Alley: Flow-law Hypotheses For Ice-sheet Modelingmentioning

confidence: 99%

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Flow-law hypotheses for ice-sheet modeling

1992

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Anisotropy and crystalline fabric of Whillans Ice Stream (West Antarctica) inferred from multicomponent seismic data

et al. 2015

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Crystal orientation fabric (COF) describes the intrinsic anisotropic nature of ice and is an important parameter for modeling glacier flow. We present the results of three‐component active‐source seismic observations from the Whillans Ice Stream (WIS), a fast‐flowing ice stream in West Antarctica. Surface‐wave dispersion analysis, ray tracing, and traveltime inversion of compressional (P) and shear (S) waves reveal the presence of transversely isotropic ice with a vertical axis of symmetry (VTI) beneath approximately 65 m of isotropic firn. The ice stream is characterized by weak anisotropy, involving an average ice thickness of approximately 780 m. The analysis indicates that about 95% of the ice mass is anisotropic, and the crystalline c axes span within an average broad cone angle of 73 ± 10° with respect to the vertical axis. Moreover, the mean temperature T (below the firn) estimated from seismic data is −15 ± 5°C. These data do not show evidence of englacial seismic reflectivity, which indicates the lack of abrupt changes in the COF. The presence of azimuthal anisotropy due to transversely compressive flow or fractures aligned along a preferential direction is also excluded. We suggest that the observed VTI ice structure is typical of large ice streams in regions where basal sliding and bed deformation dominate over internal glacial deformation.

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Deformation of debris-ice mixtures

Moore

2014

Rev. Geophys.

106

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Mixtures of rock debris and ice are common in high-latitude and high-altitude environments and are thought to be widespread elsewhere in our solar system. In the form of permafrost soils, glaciers, and rock glaciers, these debris-ice mixtures are often not static but slide and creep, generating many of the landforms and landscapes associated with the cryosphere. In this review, a broad range of field observations, theory, and experimental work relevant to the mechanical interactions between ice and rock debris are evaluated, with emphasis on the temperature and stress regimes common in terrestrial surface and near-surface environments. The first-order variables governing the deformation of debris-ice mixtures in these environments are debris concentration, particle size, temperature, solute concentration (salinity), and stress. A key observation from prior studies, consistent with expectations, is that debris-ice mixtures are usually more resistant to deformation at low temperatures than their pure end-member components. However, at temperatures closer to melting, the growth of unfrozen water films at ice-particle interfaces begins to reduce the strengthening effect and can even lead to profound weakening. Using existing quantitative relationships from theoretical and experimental work in permafrost engineering, ice mechanics, and glaciology combined with theory adapted from metallurgy and materials science, a simple constitutive framework is assembled that is capable of capturing most of the observed dynamics. This framework highlights the competition between the role of debris in impeding ice creep and the mitigating effects of unfrozen water at debris-ice interfaces.

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A review of ice rheology for ice sheet modelling

Cited by 441 publications

References 86 publications

Flow-law hypotheses for ice-sheet modeling

Flow-law hypotheses for ice-sheet modeling

Anisotropy and crystalline fabric of Whillans Ice Stream (West Antarctica) inferred from multicomponent seismic data

Deformation of debris-ice mixtures

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