Calving processes and the dynamics of calving glaciers

Benn, Douglas I.; Warren, Charles R.; Mottram, Ruth

doi:10.1016/j.earscirev.2007.02.002

Cited by 624 publications

(833 citation statements)

References 165 publications

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“…This has given rise to a semi-empirical height-above-buoyancy 'calving law' in which the ice thickness at the terminus is assumed to require a minimum or critical height-above-buoyancy or they will disintegrate (Meier & Post 1987;Van der Veen 1996, 2002Nick et al 2009Nick et al , 2010. Despite significant efforts (Benn et al 2007), no physical explanation for this type of behaviour has been found. Moreover, height-above-buoyancy calving laws do not permit the formation of floating ice tongues.…”

Section: Introductionmentioning

confidence: 99%

“…Previous attempts to model the failure of glacier ice have focused on tensile fractures (crevasses), assuming that an iceberg will detach when either a surface crevasse or a bottom crevasse penetrates the entire ice thickness or some critical fraction thereof (Weertman 1980;Rist et al 2002;Benn et al 2007;Nick et al 2010). The depth to which crevasses penetrate can be estimated using the Nye zero-stress model in which surface (d s ) and bottom (d b ) crevasses penetrate to the depth where the net horizontal stress vanishes (Nye 1957;Jezek 1984;Nick et al 2010),…”

Section: Model Description (A) Stress Near the Terminus Of A Glaciermentioning

confidence: 99%

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Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice

2011

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Observations indicate that substantial changes in the dynamics of marine-terminating ice sheets and glaciers are tightly coupled to calving-induced changes in the terminus position. However, the calving process itself remains poorly understood and is not well parametrized in current numerical ice sheet models. In this study, we address this uncertainty by deriving plausible upper and lower limits for the maximum stable ice thickness at the calving face of marine-terminating glaciers, using two complementary models. The first model assumes that a combination of tensile and shear failure can render the ice cliff near the terminus unstable and/or enable pre-existing crevasses to intersect. A direct consequence of this model is that thick glaciers must terminate in deep water to stabilize the calving front, yielding a predicted maximum ice cliff height that increases with increasing water depth, consistent with observations culled from glaciers in West Greenland, Antarctica, Svalbard and Alaska. The second model considers an analogous lower limit derived by assuming that the ice is already fractured and fractures are lubricated by pore pressure. In this model, a floating ice tongue can only form when the ice entering the terminus region is relatively intact with few pre-existing, deeply penetrating crevasses.

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Section: Introductionmentioning

confidence: 99%

Section: Model Description (A) Stress Near the Terminus Of A Glaciermentioning

confidence: 99%

Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice

2011

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“…The switch from a land-to a water-terminating ice front introduces a calving component into the mass balance of these glaciers and transforms their dynamics and climatic sensitivity [Kirkbride and Warren, 1999], generally leading to rapid ice loss [Chinn, 1996;Benn et al, 2007;Larsen et al, 2007]. The formation of proglacial lakes is an efficient means of eroding a glacier front because of submarine melting due to warm lake waters [Rohl, 2006;Paul et al, 2007].…”

Section: Factors Contributing To the Asymmetrical Ice Wastagementioning

confidence: 99%

Ice wastage on the Kerguelen Islands (49°S, 69°E) between 1963 and 2006

Berthier¹,

Bris²,

Mabileau³

et al. 2009

J. Geophys. Res.

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International audienceWe observed the wastage of ice masses on the Kerguelen Islands (Indian Ocean, 49°S, 69°E) using historical information and recent satellite data. Overall, the total ice-covered area on the islands declined from 703 to 552 km2 between 1963 and 2001, a reduction of 21%. The area of Cook ice cap (the main ice body) decreased asymmetrically from 501 to 403 km2. West-flowing glaciers lost 11% of their area while east-flowing glaciers lost 28%. After 1991, the retreat rate accelerated from 1.9 km2/yr (1963-1991) to 3.8 km2/yr (1991-2003). Between 1963 and 2000, the ice volume loss was 25-30 km3, equivalent to an area-average ice thinning rate of 1.4-1.7 m/yr. The glacial retreat took place in the climatic context of a relatively low level of precipitation (compared to the 1950s) and a ~1°C warming that occurred between 1964 and 1982. The acceleration of the ice losses since, at least, the 1990s indicates that the state of the ice bodies on the Kerguelen Islands is still far from balanced. Together with other studies in Patagonia, South Georgia and Heard Island, our analysis is consistent with a pattern of strong and accelerated wastage of ice masses influenced by the Southern Ocean

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“…In previous modelling work ( Van der Veen, 2002;Benn et al, 2007;Amundson and Truffer, 2010;Nick et al, 2010;Cook et al, 2012;Krug et al, 2014Krug et al, , 2015, the dynamics of ice masses have been simulated using continuum models, in which the continuum space is discretised and includes processes of mass and energy balance. In addition to the lack of process understanding, continuum models cannot explicitly model fracture but must use simple parameterisations such as damage variables or phenomenological calving criteria.…”

Section: Introductionmentioning

confidence: 99%

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

et al. 2018

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Abstract. In this paper, we study the effects of basal friction, sub-aqueous undercutting and glacier geometry on the calving process by combining six different models in an offlinecoupled workflow: a continuum-mechanical ice flow model (Elmer/Ice), a climatic mass balance model, a simple subglacial hydrology model, a plume model, an undercutting model and a discrete particle model to investigate fracture dynamics (Helsinki Discrete Element Model, HiDEM). We demonstrate the feasibility of reproducing the observed calving retreat at the front of Kronebreen, a tidewater glacier in Svalbard, during a melt season by using the output from the first five models as input to HiDEM. Basal sliding and glacier motion are addressed using Elmer/Ice, while calving is modelled by HiDEM. A hydrology model calculates subglacial drainage paths and indicates two main outlets with different discharges. Depending on the discharge, the plume model computes frontal melt rates, which are iteratively projected to the actual front of the glacier at subglacial discharge locations. This produces undercutting of different sizes, as melt is concentrated close to the surface for high discharge and is more diffuse for low discharge. By testing different configurations, we show that undercutting plays a key role in glacier retreat and is necessary to reproduce observed retreat in the vicinity of the discharge locations during the melting season. Calving rates are also influenced by basal friction, through its effects on near-terminus strain rates and ice velocity.

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Calving processes and the dynamics of calving glaciers

Cited by 624 publications

References 165 publications

Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice

Upper and lower limits on the stability of calving glaciers from the yield strength envelope of ice

Ice wastage on the Kerguelen Islands (49°S, 69°E) between 1963 and 2006

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

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