Pressure sintering of ice and its implication to the densification of snow at polar glaciers and ice sheets

Maeno, Norikazu; Ebinuma, Takao

doi:10.1021/j100244a023

Cited by 152 publications

(171 citation statements)

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“…As shown by Maeno (1982) and by Arzt and others (1983), diffusional creep is not an efficient mechanism of densification for the intermediate stage and for the major portion of the final stage . Several factors which have not been taken into account can influence the densification rate (Maeno and Ebinuma 1983). The most important is probably grain growth.…”

Section: Discussionmentioning

confidence: 99%

Grain Growth and Mechanical Behaviour of Polar Ice

Duval

1985

A. Glaciology.

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Crystal size in polar ice caps increases with depth from the snow surface down to several hundred meters. Data on crystal growth in isothermal polar snow and ice show the same linear relationship between the size of crystals and their age . This paper reviews the mechanical behavior of polar ice which exhibits grain growth. Grain boundary migration associated with grain growth appears to be an efficient accomoda tion process for grain boundary sliding and dislocation glide. For grain growth to occur, strain energy must always be lower than the free energy of boundaries. The sintering of ice particles in polar firn is energized by the pressure due to the overburden of snow. Dislocation creep must be taken into account to explain the densification rate in the intermediate and final stage. Constants of power law creep should depend on the crystal growth rate.

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Section: Discussionmentioning

confidence: 99%

Grain Growth and Mechanical Behaviour of Polar Ice

Duval

1985

A. Glaciology.

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“…As for many other granular materials, further densification requires the plastic deformation of the grains themselves. Above 550 kg m −3 , dislocation creep becomes the dominant mechanism for densification (Maeno and Ebinuma, 1983). The last stage of densification is porosity related.…”

Section: A Burr Et Al: X-ray Tomography Of Polar Firnmentioning

confidence: 99%

“…The SSA is defined as the surface of the pores over the total sample volume. The surface is computed with the marching cube algorithm (Lorensen and Cline, 1987). The SSA is used to quantify the air-ice interactions (e.g., to compute the snow-to-atmosphere flux of adsorbed molecules on snow; Domine et al, 2008) or to work out the grain size of firn cores (Linow et al, 2012).…”

Section: Reconstruction and Image Processingmentioning

confidence: 99%

Pore morphology of polar firn around closure revealed by X-ray tomography

et al. 2018

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Abstract. Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases. The progressive microstructure evolution of the firn column with depth leads to pore closure and gas entrapment. Air transport models in the firn usually include a closed porosity profile based on available data. Pycnometry or melting-refreezing techniques have been used to obtain the ratio of closed to total porosity and air content in closed pores, respectively. Xray-computed tomography is complementary to these methods, as it enables one to obtain the full pore network in 3-D. This study takes advantage of this nondestructive technique to discuss the morphological evolution of pores on four different Antarctic sites. The computation of refined geometrical parameters for the very cold polar sites Dome C and Lock In (the two Antarctic plateau sites studied here) provides new information that could be used in further studies. The comparison of these two sites shows a more tortuous pore network at Lock In than at Dome C, which should result in older gas ages in deep firn at Lock In. A comprehensive estimation of the different errors related to X-ray tomography and to the sample variability has been performed. The procedure described here may be used as a guideline for further experimental characterization of firn samples. We show that the closed-to-total porosity ratio, which is classically used for the detection of pore closure, is strongly affected by the sample size, the image reconstruction, and spatial heterogeneities. In this work, we introduce an alternative parameter, the connectivity index, which is practically independent of sample size and image acquisition conditions, and that accurately predicts the close-off depth and density. Its strength also lies in its simple computation, without any assumption of the pore status (open or close). The close-off prediction is obtained for Dome C and Lock In, without any further numerical simulations on images (e.g., by permeability or diffusivity calculations).

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“…The energy reduction is caused by mass transport processes such as vapour diffusion (Neumann et al, 2009), surface diffusion (Kingery, 1960b), volume diffusion (Kuroiwa, 1961), and grain boundary diffusion (Colbeck, 1997a(Colbeck, , 1998(Colbeck, , 2001Kaempfer and Schneebeli, 2007). Viscous or plastic flow (Kingery, 1960a), and sublimation condensation with vapour transport (German, 1996;Hobbs and Mason, 1963;Legagneux and Domine, 2005;Maeno and Ebinuma, 1983) are also suggested to play an important role. The Kelvin effect is seen as the driving force for isothermal snow metamorphism (Bader et al, 1939;Colbeck, 1980).…”

Section: Introductionmentioning

confidence: 99%

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

Ebner

Schneebeli²,

Steinfeld

2015

The Cryosphere

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Abstract. Time-lapse X-ray microtomography was used to investigate the structural dynamics of isothermal snow metamorphism exposed to an advective airflow. The effect of diffusion and advection across the snow pores on the snow microstructure were analysed in controlled laboratory experiments and possible effects on natural snowpacks discussed. The 3-D digital geometry obtained by tomographic scans was used in direct pore-level numerical simulations to determine the effective permeability. The results showed that isothermal advection with saturated air have no influence on the coarsening rate that is typical for isothermal snow metamorphism. Isothermal snow metamorphism is driven by sublimation deposition caused by the Kelvin effect and is the limiting factor independently of the transport regime in the pores.

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Pressure sintering of ice and its implication to the densification of snow at polar glaciers and ice sheets

Cited by 152 publications

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Grain Growth and Mechanical Behaviour of Polar Ice

Grain Growth and Mechanical Behaviour of Polar Ice

Pore morphology of polar firn around closure revealed by X-ray tomography

Tomography-based monitoring of isothermal snow metamorphism under advective conditions

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