Iceberg calving from floating glaciers by a vibrating mechanism

Holdsworth, G.; Glynn, J

doi:10.1038/274464a0

Cited by 78 publications

(114 citation statements)

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“…Several authors have suggested that calving from ice shelves and ice tongues may be triggered by flexural stresses induced by ocean swell (Holdsworth & Glynn 1978;MacAyeal et al 2006;Sergienko 2010), despite some contradictory observations that ice shelf rift propagation itself is not influenced by ocean swell (Bassis et al 2007(Bassis et al , 2008. To examine the role of ocean swell in generating transient stresses that contribute to failure of floating ice tongues, we estimated the magnitude of the horizontal stress induced in the ice following the order of magnitude estimation procedure described by Bassis et al (2007Bassis et al ( , 2008.…”

Section: (D) the Role Of Ocean Swell In Triggering Calving Events Fromentioning

confidence: 99%

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: (D) the Role Of Ocean Swell In Triggering Calving Events Fromentioning

confidence: 99%

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

2011

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“…It is however illustrative of the general lack of attention given to problems of calving of ice shelves and ice tongues that in 1977 he did not list two other processes which to the author seem to be dominant. Our second process is mentioned in Holdsworth and Glynn ( 1978) . The first process is creep failure due to lateral spreading.…”

Section: Tidal Bending Of the Flotation Line Of Ice Shelvesmentioning

confidence: 99%

“…This could lead to bending stress maxima occurring at roughly regular intervals along the length of the shelf ... ". Holdsworth and Glynn ( 1978) are continuing to investigate item (7). It is however illustrative of the general lack of attention given to problems of calving of ice shelves and ice tongues that in 1977 he did not list two other processes which to the author seem to be dominant.…”

Section: Tidal Bending Of the Flotation Line Of Ice Shelvesmentioning

confidence: 99%

Formation, Flow, and Disintegration Of Ice Shelves

Robin¹

1979

J. Glaciol.

174

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ABSTRACT. I ce shelves may develop either by continued thickening of sea ice tha t is held fast to the shore, or by the seaward extension of inla nd ice. For both p rocesses, as well as for an understanding of ablation and of accumula t ion a t the bottom surface of ice shelves, we n eed to understand melting and freezing processes in relation to salinity, temperature, and pressure. Consideration of these factors shows that b asal m elting beneath the thicker p a rts of ice shelves is much greater tha n is generally apprecia ted . This could b e sufficient to bring the estimated mass balance of Antarctica into a pproximate equilibrium. It appears that most Antarctic ice shelves are dependent on the supply of inla nd ice for their continued existence. However the thick layer of sea ice b eneath the Am ery I ce Shelf is readily explained in terms of sub-ice water circula tion.T ransport of h eat a nd mass by water m otion beneath ice shelves has the potential to change ice thicknesses by similar amounts to that caused by internal deformatio n of the ice shelf. Bottom freezing due to thermal conduction througho ut the ice shelf is of minor importa n ce.While attentio n is drawn to the basic equations for fl ow of ice shelves, it is pointed out that they have yet to be applied satisfacto rily to the problem of iceberg calving. This appears from field observations to be due primarily to creep fa ilure of spreading ice shelves, possibly a ided by impact from floating icebergs. R ecent observations show the effectiveness a nd likely quantitative importance of this " big bang" theory of iceberg for mation in Anta rctica.A brief discussio n of the effects of climatic change on the disintegration of ice shelves is presented . R ESUME. Formation, ecoulement et disp arition des platiformes de glace. Les pla teformes de glace p euvent se d evelopper soit p a r epaississement continu de la glace d e m er qui se soude solidement au rivage ou par I'extension vers la m er de la glace recou vra nt une ile. Pour les d eux processus comme pour l'intelligen ce de I'ablation et de I'accumulation a la face inferieure de la b a nquise, nous devons comprendre les m ecanismes lia nt la fusion et le regel a la salinite, a la temperature et a la pression. Des considerations sur l'action de ces facteurs montrent que la fusion a la base sous les parties les plus epaisses de la couverture de glace est b eaucoup plus importa nte qu' o n ne la pensait. Ce phenomene pourra it suffire a faire p asser I'estimation du bila n de masse de l'Anta rctique a un equilibre approximatif. Il semble que la plus gra nd e partie des plateformes de glace Antarctique d ep end pour lui p ermettre de subsister d e \'a pport de la glace continentale. Cep endant I'epaisse couche d e glace de mer sous le Amery I ce Shelf p eut facilement s'expliquer par une circula tion d'eau sous la glace.Les transpor ts d e cha leur et de m asse p ar mouvement d e I'eau sous les pla teformes de glace sont capables de modifier \' ep a isseur de glace da ns les m emes proportio n s q...

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“…For instance, it has been suggested that flexuralgravity waves may trigger rift propagation (Holdsworth and Glynn, 1978;Goodman and others, 1980), a theory that was resurrected when MacAyeal and others (2007) noticed that the break-up of iceberg B15A correlated with the arrival of a large pulse of ocean swell. Vertical tidal oscillations may bend the ice, inducing stresses that, if large enough, may trigger rift propagation.…”

Section: Introductionmentioning

confidence: 99%

An investigation into the forces that drive ice-shelf rift propagation on the Amery Ice Shelf, East Antarctica

Bassis¹,

Fricker²,

Coleman

et al. 2008

J. Glaciol.

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During these campaigns we detected seven bursts of episodic rift propagation. To determine whether these rift propagation events were triggered by short-term environmental forcings, we analyzed simultaneous ancillary data such as wind speeds, tidal amplitudes and sea-ice fraction (a proxy variable for ocean swell). We find that none of these environmental forcings, separately or together, correlated with rift propagation. This apparent insensitivity of ice-shelf rift propagation to short-term environmental forcings leads us to suggest that the rifting process is primarily driven by the internal glaciological stress. Our hypothesis is supported by order-of-magnitude calculations that the glaciological stress is the dominant term in the force balance. However, our calculations also indicate that as the ice shelf thins or the rift system matures and iceberg detachment becomes imminent, shortterm stresses due to winds and ocean swell may become more important.

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Iceberg calving from floating glaciers by a vibrating mechanism

Cited by 78 publications

References 7 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

Formation, Flow, and Disintegration Of Ice Shelves

An investigation into the forces that drive ice-shelf rift propagation on the Amery Ice Shelf, East Antarctica

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