Bounds on the calving cliff height of marine terminating glaciers

Ma, Y.; Tripathy, Cory S.; Bassis, J. N.

doi:10.1002/2016gl071560

Cited by 31 publications

(46 citation statements)

References 52 publications

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“…We can contrast this with the shear failure model of Bassis and Walker (2011) (see also Jacobs, 2013, andMa et al, 2017). The CD model requires d w > 0 and predicts calving for any h below the value given by Eq.…”

Section: Calving Modelmentioning

confidence: 95%

“…In addition, the stress fields considered by Weertman (1973Weertman ( , 1980, van der Veen (1998a, b) and Nick et al (2010) are relatively simple and apply only at distances significantly greater than a single ice thickness from the calving front. In the calving of shorter, taller icebergs, torques near the calving front (Hanson and Hooke, 2000;Ma et al, 2017) may allow calving when purely extensional stresses experienced further upstream do not.…”

Section: Calving Modelmentioning

confidence: 99%

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Boundary layer models for calving marine outlet glaciers

2017

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Abstract. We consider the flow of marine-terminating outlet glaciers that are laterally confined in a channel of prescribed width. In that case, the drag exerted by the channel side walls on a floating ice shelf can reduce extensional stress at the grounding line. If ice flux through the grounding line increases with both ice thickness and extensional stress, then a longer shelf can reduce ice flux by decreasing extensional stress. Consequently, calving has an effect on flux through the grounding line by regulating the length of the shelf. In the absence of a shelf, it plays a similar role by controlling the above-flotation height of the calving cliff. Using two calving laws, one due to Nick et al. (2010) based on a model for crevasse propagation due to hydrofracture and the other simply asserting that calving occurs where the glacier ice becomes afloat, we pose and analyse a flowline model for a marine-terminating glacier by two methods: direct numerical solution and matched asymptotic expansions. The latter leads to a boundary layer formulation that predicts flux through the grounding line as a function of depth to bedrock, channel width, basal drag coefficient, and a calving parameter. By contrast with unbuttressed marine ice sheets, we find that flux can decrease with increasing depth to bedrock at the grounding line, reversing the usual stability criterion for steady grounding line location. Stable steady states can then have grounding lines located on retrograde slopes. We show how this anomalous behaviour relates to the strength of lateral versus basal drag on the grounded portion of the glacier and to the specifics of the calving law used.

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Section: Calving Modelmentioning

confidence: 95%

Section: Calving Modelmentioning

confidence: 99%

Boundary layer models for calving marine outlet glaciers

2017

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“…As described in Ma et al (), the full Stokes system we are solving can be represented as the conservation of linear momentum in both x and z directions and the incompressibility of glacier ice:

\frac{\partial τ_{x x}}{\partial x} + \frac{\partial τ_{x z}}{\partial z} = \frac{\partial p}{\partial x},

\frac{\partial τ_{x z}}{\partial x} + \frac{\partial τ_{z z}}{\partial z} = \frac{\partial p}{\partial z} + ρ_{i} g,

\frac{\partial u}{\partial x} + \frac{\partial w}{\partial z} = 0 .

…”

Section: Model Descriptionmentioning

confidence: 99%

“…In the section above we have focused on the deviatoric stress. However, the failure criteria are based on the Cauchy stress and we examine both tensile and shear stresses (Ma et al, ). The relationship between Cauchy stress σ and deviatoric stress τ is simple:

σ_{i j} = τ_{i j} - p δ_{i j}

where p is the pressure and δ ij is the Kronecker delta.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The initial thickness of the glacier is set to 800 m, as a representative size of major marine terminating glaciers in Greenland and Alaska (e.g., Jakobshavn, Helheim Glacier). Based on our failure criterion, only a range of ice thickness/water depth combinations are permissible at the calving front or the glacier will develop through‐penetrating fractures immediately, resulting in disintegration (Ma et al, ). This envelope of ice thickness/water depth combinations also agrees with observations around Greenland (Bassis & Walker, ; Ma et al, ).…”

Section: Model Descriptionmentioning

confidence: 99%

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The Effect of Submarine Melting on Calving From Marine Terminating Glaciers

Bassis

2019

JGR Earth Surface

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Submarine melting and iceberg calving are two important processes that control mass loss from the terminus of tidewater glaciers. There have been significant efforts to quantify the effect of submarine melting on glacier calving, but controversy remains with conflicting studies indicating submarine melting can increase, decrease, or has minimal effect on calving. Here we show using a two‐dimensional full Stokes finite element model that submarine melt can alter the state of stress near the terminus and the changes in stress exert a first‐order control on the calving regime of marine terminating glaciers. The model calculates both the largest principal and maximum shear stresses and then maps out where tensile and shear failure occur for a range of melt rates and vertical melt profiles. We find that submarine melt initially promotes full thickness calving events. However, as the melt rate further increases, an overhang begins to form and resulting compressive stresses suppress full thickness calving. These results are relatively insensitive to basal friction. Moreover, our results suggest that submarine melting can both increase and decrease calving rates with the magnitude and sign of the effect determined by the shape of the melt profile and the relative magnitude of average melt rate. Despite the fact that calving is suppressed in some circumstances, the addition of submarine melt almost always increases the total mass loss. Overall, we find that relatively small amounts of submarine melt can destabilize glaciers, but calving and frontal ablation are increasingly controlled by submarine melt as it continues to increase.

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Future sea level change from Antarctica's Lambert‐Amery glacial system

Pittard

Watson

Roberts

2017

Geophysical Research Letters

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Future global mean sea level (GMSL) change is dependent on the complex response of the Antarctic ice sheet to ongoing changes and feedbacks in the climate system. The Lambert‐Amery glacial system has been observed to be stable over the recent period yet is potentially at risk of rapid grounding line retreat and ice discharge given that a significant volume of its ice is grounded below sea level, making its future contribution to GMSL uncertain. Using a regional ice sheet model of the Lambert‐Amery system, we find that under a range of future warming and extreme scenarios, the simulated grounding line remains stable and does not trigger rapid mass loss from grounding line retreat. This allows for increased future accumulation to exceed the mass loss from ice dynamical changes. We suggest that the Lambert‐Amery glacial system will remain stable or gain ice mass and mitigate a portion of potential future sea level rise over the next 500 years, with a range of +3.6 to −117.5 mm GMSL equivalent.

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Bounds on the calving cliff height of marine terminating glaciers

Cited by 31 publications

References 52 publications

Boundary layer models for calving marine outlet glaciers

Boundary layer models for calving marine outlet glaciers

The Effect of Submarine Melting on Calving From Marine Terminating Glaciers

Future sea level change from Antarctica's Lambert‐Amery glacial system

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