Modeling ice‐ocean interaction in ice‐shelf crevasses

Jordan, James; Holland, Paul R.; Jenkins, Adrian; Piggott, Matthew D.; Kimura, Satoshi

doi:10.1002/2013jc009208

Cited by 24 publications

(42 citation statements)

References 40 publications

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“…Such models rely on previous theoretical work concerning frazil-ice dynamics, which was pioneered by Daly (1984). Models of frazilice dynamics have been applied to the study of frazil in the upper ocean Omstedt, 1994, 1998;Heorton et al, 2017) and also to the study of frazil ice beneath ice shelves (Jenkins and Bombosch, 1995;Khazendar and Jenkins, 2003;Smedsrud and Jenkins, 2004;Holland and Feltham, 2005;Jordan et al, 2014Jordan et al, , 2015. The theory of frazil-ice dynamics involves parameterizations of a number of physical processes that affect the evolution of a population of ice crystals.…”

Section: Frazil Ice In the Environmentmentioning

confidence: 99%

“…These papers are illustrative of a wider range of studies (e.g. Svensson and Omstedt, 1998;Khazendar and Jenkins, 2003;Holland and Feltham, 2005;Jordan et al, 2014Jordan et al, , 2015Wilchinsky et al, 2015;Smedsrud and Martin, 2015); recently it appears that growth law f 3 has been used most commonly, if not exclusively. In summary, numerical calculations show that there is only weak dependence on aspect ratio: f 1 is typically close to f 2 ; however, f 1 is some 10-100 times greater than f 3 , as illustrated in Fig.…”

Section: Crystal Growth Ratementioning

confidence: 99%

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Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

Jones

Wells

2018

The Cryosphere

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Abstract. The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest that crystals grow much faster than previously thought. In this paper, we consider models of a population of ice crystals with different sizes to provide insight into the treatment of frazil ice in large-scale models. We consider the role of crystal growth alongside the other physical processes that determine the dynamics of frazil ice. We apply our model to a simple mixed layer (such as at the surface of the ocean) and to a buoyant plume under a floating ice shelf. We provide numerical calculations and scaling arguments to predict the occurrence of frazil-ice explosions, which we show are controlled by crystal growth, nucleation, and gravitational removal. Faster crystal growth, higher secondary nucleation, and slower gravitational removal make frazil-ice explosions more likely. We identify steady-state crystal size distributions, which are largely insensitive to crystal growth rate but are affected by the relative importance of secondary nucleation to gravitational removal. Finally, we show that the fate of plumes underneath ice shelves is dramatically affected by frazil-ice dynamics. Differences in the parameterization of crystal growth and nucleation give rise to radically different predictions of basal accretion and plume dynamics, and can even impact whether a plume reaches the end of the ice shelf or intrudes at depth.

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Section: Frazil Ice In the Environmentmentioning

confidence: 99%

Section: Crystal Growth Ratementioning

confidence: 99%

Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

Jones

Wells

2018

The Cryosphere

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“…The evolution of basal fractures predicted here by the KPZ equation neglects spatial variations in melt rate across the ice shelf (e. g. Gwyther et al, 2014;Roberts et al, 2017), as well as variations in melt rate which have been predicted to occur within 15 basal features (Jordan et al, 2014;Millgate et al, 2013). It also does not include the effects of internal ice deformation and strain thinning, which are particularly significant near the calving front where the ice shelf is unconfined and spreads laterally.…”

Section: Fracture Advectionmentioning

confidence: 99%

“…Basal crevasses have been observed near the grounding line of ice shelves 5 (e.g. Bindschadler et al, 2011b;Jacobel et al, 2014) and may evolve in shape and size as they advect downstream (Jordan et al, 2014). To fully understand the calving behaviour of an ice shelf, we must therefore understand how fractures form and propagate on it.…”

Section: Introductionmentioning

confidence: 99%

Modelled fracture and calving on the Totten Ice Shelf

Cook¹,

Åström²,

Zwinger³

et al. 2018

Preprint

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Abstract. The Totten Ice Shelf (IS) has a large drainage basin, much of which is grounded below sea level, leaving the glacier vulnerable to retreat through the Marine Ice Shelf Instability mechanism. The ice shelf has also been shown to be sensitive to changes in calving rate, as a very small retreat of the calving front from its current position is predicted to cause a change in flow at the grounding line. Therefore understanding the processes behind calving on the Totten IS is key to predicting its future sea level rise contribution. Here we use the Helsinki Discrete Element Model (HiDEM) to show that calving on the Totten IS 15 is controlled not only by locally produced fractures at the calving front, but is also influenced by basal fractures which are likely produced at the grounding line. Our model results show that regrounding points may be key areas of basal crevasse production, and can produce basal crevasses in both an along and across flow orientation. As well as affecting calving, along flow basal crevasses at the grounding line may be a possible precursor to basal channels. We use two additional models to examine the evolution of basal fractures as they advect downstream, demonstrating that both strain and ocean melt have the 20 potential to deform narrow fractures into the broad basal features observed near the calving front. The wide range of factors which influence fracture patterns and calving on this glacier will be a challenge for predicting its future mass loss.

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“…The variable w c is the melt rate of frazil ice per unit volume of mixture, and it is therefore negative during ice formation (Jenkins and Bombosch 1995). While the use of w c to denote melt rate may be considered confusing, since frazil crystal rising velocity is denoted w i , it has been used in previous work using the frazil ice model of Jenkins and Bombosch (1995) (Khazendar and Jenkins 2003;Holland and Feltham 2005;Jordan et al 2014) and so has been used to maintain consistency. The second term on the right-hand sides of (4) and (5) accounts for the temperature and salinity changes in a fixed volume of the water fraction because of the frazil phase change (Holland and Feltham 2005).…”

Section: Governing Equationsmentioning

confidence: 99%

On the Conditional Frazil Ice Instability in Seawater

Jordan

Kimura

Holland

et al. 2015

Journal of Physical Oceanography

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It has been suggested that the presence of frazil ice can lead to a conditional instability in seawater. Any frazil forming in the water column reduces the bulk density of a parcel of frazil-seawater mixture, causing it to rise. As a result of the pressure decrease in the freezing point, this causes more frazil to form, causing the parcel to accelerate, and so on. This study uses linear stability analysis and a nonhydrostatic ocean model to study this instability. The authors find that frazil ice growth caused by the rising of supercooled water is indeed able to generate a buoyancy-driven instability. Even in a gravitationally stable water column, the frazil ice mechanism can still generate convection. The instability does not operate in the presence of strong density stratification, high thermal driving (warm water), a small initial perturbation, high background mixing, or the prevalence of large frazil ice crystals. In an unstable water column, the instability is not necessarily expressed in frazil ice at all times; an initial frazil perturbation may melt and refreeze. Given a large enough initial perturbation, this instability can allow significant ice growth. A model shows frazil ice growth in an Ice Shelf Water plume several kilometers from an ice shelf, under similar conditions to observations of frazil ice growth under sea ice. The presence of this instability could be a factor affecting the growth of sea ice near ice shelves, with implications for Antarctic Bottom Water formation.

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Modeling ice‐ocean interaction in ice‐shelf crevasses

Cited by 24 publications

References 40 publications

Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

Modelled fracture and calving on the Totten Ice Shelf

On the Conditional Frazil Ice Instability in Seawater

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