Fracture-induced softening for large-scale ice  dynamics

Albrecht, Torsten; Levermann, Anders

doi:10.5194/tc-8-587-2014

Cited by 44 publications

(64 citation statements)

References 79 publications

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“…It is also clear that the Nye zero stress model cannot be the whole story: if nothing else it requires a phenomenological parameter (the crevasse water depth) to treat calving events, which may in effect be standing in for entirely different physics, such as brittle failure (Krug et al, 2014). It may be important to consider a threshold stress for damage initiations and mechanisms of crevasse healing (Albrecht and Levermann, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…Models in this category (Nick et al, 2010(Nick et al, , 2013Cook et al, 2014) compute crevasse depth based on instantaneous fields and hence do not take into account the stress history in the development of fractures. Models in the second category use a continuum damage mechanics (CDM) approach, which treats calving as a continuum process that develops from microscale cracks to macroscale crevasses, and damage has an effect on the viscous behaviour of ice flow (Pralong and Funk, 2005;Jouvet et al, 2011;Duddu and Waisman, 2012;Borstad et al, 2012Borstad et al, , 2013Albrecht and Levermann, 2014;Krug et al, 2014;Bassis and Ma, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Ice shelf fracture parameterization in an ice sheet model

et al. 2017

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Abstract. Floating ice shelves exert a stabilizing force onto the inland ice sheet. However, this buttressing effect is diminished by the fracture process, which on large scales effectively softens the ice, accelerating its flow, increasing calving, and potentially leading to ice shelf breakup. We add a continuum damage model (CDM) to the BISICLES ice sheet model, which is intended to model the localized opening of crevasses under stress, the transport of those crevasses through the ice sheet, and the coupling between crevasse depth and the ice flow field and to carry out idealized numerical experiments examining the broad impact on large-scale ice sheet and shelf dynamics. In each case we see a complex pattern of damage evolve over time, with an eventual loss of buttressing approximately equivalent to halving the thickness of the ice shelf. We find that it is possible to achieve a similar ice flow pattern using a simple rule of thumb: introducing an enhancement factor ∼ 10 everywhere in the model domain. However, spatially varying damage (or equivalently, enhancement factor) fields set at the start of prognostic calculations to match velocity observations, as is widely done in ice sheet simulations, ought to evolve in time, or grounding line retreat can be slowed by an order of magnitude.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ice shelf fracture parameterization in an ice sheet model

et al. 2017

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“…In the last few years, some authors have used continuum damage mechanics to represent both the development from micro-defects in the ice to the development of macro-scale crevasses, and their effects on the viscous behaviour of the ice while keeping a continuum approach (Duddu and Waisman, 2012;Borstad et al, 2012;Albrecht and Levermann, 2014). Initially developed for metal deformation (Kachanov, 1958), damage mechanics has recently been applied to ice dynamics to study the appearance of a single crevasse (Pralong et al, 2003;Pralong and Funk, 2005;Duddu and Waisman, 2013) or to average crevasse fields (Borstad et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Combining damage and fracture mechanics to model calving

et al. 2014

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Abstract.Calving of icebergs is a major negative component of polar ice-sheet mass balance. Here we present a new calving model relying on both continuum damage mechanics and linear elastic fracture mechanics. This combination accounts for both the slow sub-critical surface crevassing and the rapid propagation of crevasses when calving occurs. First, damage to the ice occurs over long timescales and enhances the viscous flow of ice. Then brittle fractures propagate downward, at very short timescales, when the ice body is considered as an elastic medium. The model was calibrated on Helheim Glacier, Southeast Greenland, a well-monitored glacier with fast-flowing outlet. This made it possible to identify sets of model parameters to enable a consistent response of the model and to produce a dynamic equilibrium in agreement with the observed stable position of the Helheim ice front between 1930 and today.

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“…This law only relies on tensile stresses and does not include all of the processes that may yield to calving (such as damage, hydro-fracture, or bending), but it has shown encouraging results on some Greenland glaciers Choi et al, 2017). Recently, several studies have developed new approaches based on a continuum damage model (Duddu et al, 2013;Albrecht and Levermann, 2014) or linear elastic fracture mechanics (LEFM) (Yu et al, 2017), and Krug 15 et al (2014) combined damage and fracture mechanics to model calving dynamics in Greenland. These studies investigated fracture formation and propagation involved in calving, but have only focused so far on individual calving events in small-scale cases, and it is not clear how to extend these studies to three-dimensional large scale models of Greenland.…”

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confidence: 99%

Comparison of four calving laws to model Greenland outlet glaciers

Choi¹,

Morlighem²,

Wood³

et al. 2018

Preprint

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Abstract. Calving is an important mechanism that controls the dynamics of marine terminating glaciers of Greenland. Iceberg calving at the terminus affects the entire stress regime of outlet glaciers, which may lead to further retreat and ice flow acceleration. It is therefore critical to accurately parameterize calving in ice sheet models in order to improve the projections of ice sheet change over the coming decades and reduce the uncertainty in their contribution to sea level rise. Several calving laws have been proposed, but most of them have been applied only to a specific region and have not been tested on other 5 glaciers, while some others have only been implemented in one-dimensional flowline or vertical flowband models. Here, we test and compare several calving laws recently proposed in the literature using the Ice Sheet System Model (ISSM). We test these calving laws on nine tidewater glaciers of Greenland. We compare the modeled ice front evolution to the observed retreat from Landsat data collected over the past 10 years, and assess which calving law has better predictive abilities for each glacier.Overall, the von Mises tensile stress calving law is more satisfactory than other laws for simulating observed ice front retreat, 10 but new parameterizations that capture better the different modes of calving should be developed. Although the final positions of ice fronts are different for forecast simulations with different calving laws, our results confirm that ice front retreat highly depends on bed topography irrespective of the calving law employed. This study also confirms that calving dynamics needs to be plan-view or 3D in ice sheet models to account for complex bed topography and narrow fjords along the coast of Greenland.

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Fracture-induced softening for large-scale ice dynamics

Cited by 44 publications

References 79 publications

Ice shelf fracture parameterization in an ice sheet model

Ice shelf fracture parameterization in an ice sheet model

Combining damage and fracture mechanics to model calving

Comparison of four calving laws to model Greenland outlet glaciers

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