The Unsolved General Glacier Sliding Problem

Weertman, J.

doi:10.1017/s0022143000029762

Cited by 51 publications

(15 citation statements)

References 31 publications

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“…McClung [, ], McClung and Clarke [], and McClung et al [] drew on the results obtained by Weertman [] and Nye [] to identify two sliding mechanisms for snowpack: the two main effects induced by free water are the reduction in snowpack viscosity and the partial separation of the snowpack base from the ground. McClung [, ] deduced that the distribution of water‐filled cavities is a function of ground roughness, and by elaborating on Nye's theory and assuming that snow behaves like a compressible viscous fluid, he ended up with a linear basal friction law:

τ_{b} = \frac{η}{2 (1 - ν)} \frac{u_{s}}{D_{h}},

…”

Section: Glide Avalanche Initiationmentioning

confidence: 99%

Dynamics of glide avalanches and snow gliding

Ancey

Bain²

2015

Reviews of Geophysics

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In recent years, due to warmer snow cover, there has been a significant increase in the number of cases of damage caused by gliding snowpacks and glide avalanches. On most occasions, these have been full-depth, wet-snow avalanches, and this led some people to express their surprise: how could low-speed masses of wet snow exert sufficiently high levels of pressure to severely damage engineered structures designed to carry heavy loads? This paper reviews the current state of knowledge about the formation of glide avalanches and the forces exerted on simple structures by a gliding mass of snow. One particular difficulty in reviewing the existing literature on gliding snow and on force calculations is that much of the theoretical and phenomenological analyses were presented in technical reports that date back to the earliest developments of avalanche science in the 1930s. Returning to these primary sources and attempting to put them into a contemporary perspective are vital. A detailed, modern analysis of them shows that the order of magnitude of the forces exerted by gliding snow can indeed be estimated correctly. The precise physical mechanisms remain elusive, however. We comment on the existing approaches in light of the most recent findings about related topics, including the physics of granular and plastic flows, and from field surveys of snow and avalanches (as well as glaciers and debris flows). Methods of calculating the forces exerted by glide avalanches are compared quantitatively on the basis of two case studies. This paper shows that if snow depth and density are known, then certain approaches can indeed predict the forces exerted on simple obstacles in the event of glide avalanches or gliding snow cover.

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τ_{b} = \frac{η}{2 (1 - ν)} \frac{u_{s}}{D_{h}},

…”

Section: Glide Avalanche Initiationmentioning

confidence: 99%

Dynamics of glide avalanches and snow gliding

Ancey

Bain²

2015

Reviews of Geophysics

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“…Classical (i.e., “hard bed”) sliding theory postulates that a layer of water at the ice‐bed interface cannot support a shear stress, so that drag at the glacier sole is generated by undulations in the topography that obstruct ice flow [ Fowler , 1981; Kamb , 1970; Weertman , 1957, 1979], as well as friction from basal debris that bridge the water layer [e.g., Iverson et al , 2003; Schweizer and Iken , 1992]. As long as these bed obstacles are small relative to the ice thickness [ Fowler , 1981], the motion of basal ice, u s , along the bed can be related to the large‐scale basal drag, τ b , as: where C and m are positive constants that are dependent on basal roughness and ice rheology.…”

Section: Introductionmentioning

confidence: 99%

Dynamic controls on glacier basal motion inferred from surface ice motion

et al. 2008

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[1] Current heuristic laws that relate the motion of glaciers due to sliding along the bed to the subglacial water pressure fail to reproduce variations in sliding speed on timescales of specific hydrologic events, such as lake drainage, rainfall, or surging. This may be due to the importance of subglacial cavity evolution and shifts in the glacier stress field, both of which are not accounted for in typical sliding laws. We use multiple time series of surface motion over a 66-day period at Brei*amerkurjökull, Iceland, to infer changes in bed separation and longitudinal force budget. We observe multiple, distinct periods of increased surface motion and uplift corresponding to periods of rainfall and/or increased temperatures. We find consistent hysteresis and lags between motion and variations in both the bed separation and longitudinal stress gradient that we attribute to the redistribution of normal stresses at the bed during cavity growth. Increases in the longitudinal stress gradient suggest a downglacier stress transfer during increased basal motion that is consistent with increased drainage system efficiency toward the terminus. Our results suggest that the transient evolution of the subglacial drainage system and shifts in the glacier stress field are important controls on basal motion.Citation: Howat, I. M., S. Tulaczyk, E. Waddington, and H. Björnsson (2008), Dynamic controls on glacier basal motion inferred from surface ice motion,

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“…The characteristics of the microphysics of basal water flow have been addresses by many workers, including Weertman (1962Weertman ( ,1966Weertman ( ,1969Weertman ( ,1970Weertman ( ,1972Weertman ( ,1979, Lliboutry (1979Lliboutry ( ,1983, Nye (1973), Rothlisberger (1972), andWalder (1982). The characteristics of the microphysics of basal water flow have been addresses by many workers, including Weertman (1962Weertman ( ,1966Weertman ( ,1969Weertman ( ,1970Weertman ( ,1972Weertman ( ,1979, Lliboutry (1979Lliboutry ( ,1983, Nye (1973), Rothlisberger (1972), andWalder (1982).…”

Section: Introductionmentioning

confidence: 99%

Numerical Modelling of the Large-Scale Basal Water Flux under the West Antarctic Ice Sheet

Budd

Jenssen

1987

Dynamics of the West Antarctic Ice Sheet

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The three-dimensional ice-sheet model of the West Antacrtic Ross Ice Shelf Basin, developed by Budd et ale (1984), has been used to compute basal temperatures and melt rates for a wide range of values of the geothermal flux. Steady state is assumed and ice "balance velocities" are computed from continuity and used in the heat-conduction equation. As the geothermal flux increases, the melt area increases and becomes connected to the water under the Ross Ice Shelf via the major ice streams.The large-scale average surface and bed slopes are used to determine the broadscale pattern of flow of the basal meltwater on the assumption that it flows as a film at the ice-bedrock interface. The total water volume flux for steady state is determined from the basal melt rates and continuity, and the film assumption then allows the mean water film thickness and velocities to be computed. The resulting pattern of steady-state mean water-film thickness is then interpreted in terms of its possible relationships to the basal sliding rates and the basal shear stress particularly under the major ice streams.C. J. van der Veen andJ. Oerlemans (eds.), Dynamics of the West Antarctic Ice Sheet, 293-320.

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The Unsolved General Glacier Sliding Problem

Cited by 51 publications

References 31 publications

Dynamics of glide avalanches and snow gliding

Dynamics of glide avalanches and snow gliding

Dynamic controls on glacier basal motion inferred from surface ice motion

Numerical Modelling of the Large-Scale Basal Water Flux under the West Antarctic Ice Sheet

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