Influence of snow type and temperature on snow viscosity

Delmas, Louis

doi:10.3189/2013jog11j231

Cited by 5 publications

(3 citation statements)

References 25 publications

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“…For single sinusoidal wavelengths, D h = λ ( λ / a ) 2 /(8 π 3 ), where λ and a denote the wavelength and amplitude of ground undulations, respectively [ McClung , ]. The linear viscous fluid assumption is a crude one: for dense snow, rheometrical tests exhibit a nonlinear viscoelastic behavior (shear thinning, with a shear thinning index close to 1/3, as in Glen's law used for ice) [ Scapozza and Bartelt , ; Delmas , ]. However, several experiments have tried to estimate bulk shear viscosity: it has usually been found that snow viscosity varies by several orders of magnitude as a function of temperature, density, and liquid water content: η ranges from 10 6 Pa s to 10 12 Pa s [ Haefeli , ; Bucher , ; Salm , ; Haefeli , ; Salm , ; Shapiro et al , ; Teufelsbauer , ]; the typical values for snow at T = 0°C with ρ = 400 kg m −3 are η ∼ 5×10 10 Pa s and ν ∼ 0.2 [ Shinojima , ; Shapiro et al , ].…”

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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Section: Glide Avalanche Initiationmentioning

confidence: 99%

Dynamics of glide avalanches and snow gliding

Ancey

Bain²

2015

Reviews of Geophysics

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“…In contrast, the series with an applied stress of 133 Pa showed a significant, steady densification of 27-48% per day, which is clearly influenced by the temperature. The temperature influence of the densification of snow is often described by an Arrhenius law (Bader, 1960;Arnaud et al, 2000;Kirchner et al, 2001;Delmas, 2013),…”

Section: Densification Ratementioning

confidence: 99%

Influence of stress, temperature and crystal morphology on isothermal densification and specific surface area decrease of new snow

Schleef¹,

Löwe²,

Schneebeli³

2014

The Cryosphere

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Abstract. Laboratory-based, experimental data for the microstructural evolution of new snow are scarce, though applications would benefit from a quantitative characterization of the main influences. To this end, we have analyzed the metamorphism and concurrent densification of new snow under isothermal conditions by means of X-ray microtomography and compiled a comprehensive data set of 45 time series. In contrast to previous measurements on isothermal metamorphism on time scales of weeks to months, we analyzed the initial 24–48 h of snow evolution at a high temporal resolution of 3 hours. The data set comprised natural and laboratory-grown snow, and experimental conditions included systematic variations of overburden stress, temperature and crystal habit to address the main influences on specific surface area (SSA) decrease rate and densification rate in a snowpack. For all conditions, we found a linear relation between density and SSA, indicating that metamorphism has an immediate influence for the densification of new snow. The slope of the linear relation, however, depends on the other parameters which were analyzed individually to derive a best-fit parameterization for the SSA decrease rate and densification rate. In the investigated parameter range, we found that the initial value of the SSA constituted the main morphological influence on the SSA decrease rate. In turn, the SSA decrease rate constituted the main influence on the densification rate.

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Section: Densification Ratementioning

confidence: 99%

Influence of stress, temperature and crystal habit on isothermal densification and specific surface area decrease of new snow

Schleef¹,

Löwe²,

Schneebeli³

2014

Preprint

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Abstract. Laboratory-based, experimental data for the microstructural evolution of new snow is scarce, though applications would benefit from a quantitative characterization of the main mechanism underlying the initial microstructural changes. To this end we have analyzed the metamorphism and concurrent densification of new snow under isothermal conditions by means of X-ray microtomography and compiled a comprehensive data set of 45 time series covering the practically relevant short time behavior within the first 24–48 h in high temporal resolution. The data set comprises natural and laboratory grown snow and experimental conditions include systematic variations of overburden stress, temperature and crystal habit to address the main influences on specific surface area (SSA) decrease rate and densification rate in a natural snowpack. For all conditions we find a linear increase of the density with the SSA, indicating that metamorphism has a key influence for the densification of new snow. Corroborated by the analysis of the individual influences of external conditions we derive a best-fit parametrization for the SSA decrease rate and the densification rate as required for applications.

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Influence of snow type and temperature on snow viscosity

Cited by 5 publications

References 25 publications

Dynamics of glide avalanches and snow gliding

Dynamics of glide avalanches and snow gliding

Influence of stress, temperature and crystal morphology on isothermal densification and specific surface area decrease of new snow

Influence of stress, temperature and crystal habit on isothermal densification and specific surface area decrease of new snow

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