Anisotropic damage mechanics for viscoelastic ice

Pralong, A.; Hutter, Kolumban; Funk, Martin

doi:10.1007/s00161-005-0002-5

Cited by 28 publications

(28 citation statements)

References 24 publications

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“…Pralong and Funk, 2005;Duddu and Waisman, 2012) as well as cohesive snow (Borstad and McClung, 2011). Pralong et al (2006) demonstrated that this equivalence scheme is thermodynamically consistent for damage as well as healing (damage reversal) of ice. We adopt this equivalence scheme here, which leads to the following definition of an effective stress,…”

Section: Linear Mapping Between Physical and Effective Spacesmentioning

confidence: 82%

Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

et al. 2013

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Abstract. Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice into the ocean, and the presently observed thinning of ice shelves is believed to be reducing their buttressing capacity and contributing to the acceleration and thinning of the grounded ice sheet. However, relatively little attention has been paid to the role that fractures play in the ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new framework for quantifying the role that fractures play in the creep deformation and buttressing capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new analytical relation for the creep of an ice shelf that accounts for the softening influence of fractures on longitudinal deformation using a state damage variable. We use this new analytical relation, combined with a temperature calculation for the ice, to partition an inverse method solution for ice shelf rigidity into independent solutions for softening damage and stabilizing backstress. Using this new approach, field and remote sensing data can be utilized to monitor the structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding line, and thus their indirect contribution to ice sheet mass balance and global sea level. We apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data, finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in this area could diminish the backstress transmitted upstream. We model the consequences for the ice shelf if it loses contact with this small ice rise, finding that flow speeds would increase by 25 % or more over an area the size of the former Larsen B ice shelf. Such a perturbation could potentially destabilize the northern part of Larsen C along pre-existing lines of weakness, highlighting the importance of the feedback between buttressing and fracturing in an ice shelf.

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Section: Linear Mapping Between Physical and Effective Spacesmentioning

confidence: 82%

Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

et al. 2013

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“…A novel suggestion to model calving may be given by damage mechanics (Pralong et al 2003(Pralong et al , 2006Pralong and Funk 2005), which may be included into full Stokes flow models. Damage denotes a continuous field that is defined by source and sink terms related to the stress field, as formulated by Pralong and Funk (2005):…”

Section: Grounded Icementioning

confidence: 99%

Present State and Prospects of Ice Sheet and Glacier Modelling

2011

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Since the late 1970s, numerical modelling has become established as an important technique for the understanding of ice sheet and glacier dynamics, and several models have been developed over the years. Ice sheet models are particularly relevant for predicting the possible response of ice sheets to climate change. Recent observations suggest that ice dynamics could play a crucial role for the contribution of ice sheets to future sea level rise under global warming conditions, and the need for further research into the matter was explicitly stated in the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC). In this paper, we review the state of the art and current problems of ice sheet and glacier modelling. An outline of the underlying theory is given, and crucial processes (basal sliding, calving, interaction with the solid Earth) are discussed. We summarise recent progress in the development of ice sheet and glacier system models and their coupling to climate models, and point out directions for future work.

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“…Different physical processes were put forward to explain this behavior: Several attempts have been made to link log‐periodic oscillations to a system that contains a relaxation mechanism reducing the damage [ Ide and Sornette , ]. However, the existence of such a relaxation mechanism in ice (negative feedback such as healing) is rather uncertain at such small time scales. The evolution of damage anisotropy in the case of a shearing fracture was proposed by Pralong [] and Pralong et al [] as a possible explanation for such an oscillating behavior. The existence of log‐periodic oscillations emerges naturally from the classic constitutive equations of anisotropic damage evolution and ice deformation in the case of shearing flow. The appearance of the log‐periodic oscillations could also result from dynamic crack interaction, as shown by Huang et al [] and Sahimi and Arbabi [].…”

Section: Instabilities Of Cold Glaciersmentioning

confidence: 99%

Avalanching glacier instabilities: Review on processes and early warning perspectives

Faillettaz

Funk

Vincent

2015

Reviews of Geophysics

101

102

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Avalanching glacier instabilities are gravity-driven rupture phenomena that might cause major disasters, especially when they are at the origin of a chain of processes. Reliably forecasting such events combined with a timely evacuation of endangered inhabited areas often constitute the most efficient action. Recently, considerable efforts in monitoring, analyzing, and modeling such phenomena have led to significant advances in destabilization process understanding, improving early warning perspectives. The purpose of this paper is to review the recent progress in this domain. Three different types of instabilities can be identified depending on the thermal properties of the ice/bed interface. If cold (1), the maturation of the rupture is associated with a typical time evolution of surface velocities and passive seismic activity. A prediction of the final break off is possible using these precursory signs. For the two other types, water plays a key role in the development of the instability. If the ice/bed interface is partly temperate (2), the presence of meltwater may reduce the basal resistance, which promotes the instability. No clear and easily detectable precursory signs are known in this case, and the only way to infer any potential instability is to monitor the temporal evolution of the thermal regime. The last type of instability (3) concerns steep temperate glacier tongues switching for several days/weeks during the melting season into a so-called "active phase" followed in rare cases by a major break-off event. Although the prediction of such events is still far from being achievable, critical conditions promoting the final instability can be identified.

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Anisotropic damage mechanics for viscoelastic ice

Cited by 28 publications

References 24 publications

Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf

Present State and Prospects of Ice Sheet and Glacier Modelling

Avalanching glacier instabilities: Review on processes and early warning perspectives

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