Melting and Refreezing in an Ice Shelf Basal Channel at the Grounding Line of the Kamb Ice Stream, West Antarctica

Whiteford, A.; Horgan, Huw; Leong, Wei Ji; Forbes, Martin

doi:10.1029/2021jf006532

Cited by 7 publications

(8 citation statements)

References 90 publications

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“…Several nonlinear effects not considered in our analysis may also influence the evolution of melt-generated ice shelf topography. For example, ice deformation effects such as proximity to the grounding line [22,60], varying ice-shelf geometry, extensional stress regimes and fracture [47,48], or viscoelasticity [45] may produce different non-hydrostatic effects relative to the purely viscous shelves considered here. We have also assumed that the melting or freezing rate is a prescribed forcing function in this model.…”

Section: Discussionmentioning

confidence: 99%

“…Although melting dominates the basal mass balance of most Antarctic ice shelves [16], altimetry, ice-penetrating radar, and numerical models have shown that many ice shelves have regions where water is freezing to the base [17][18][19][20][21][22]. Borehole drilling has shown that thick units of frozen-on marine ice exist beneath the Amery Ice Shelf [23][24][25] and the Ronne-Filchner Ice Shelf [26,27].…”

Section: Introductionmentioning

confidence: 99%

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Linear analysis of ice-shelf topography response to basal melting and freezing

Stubblefield¹,

Meyer²,

Wearing³

2023

Preprint

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Floating ice shelves in Antarctica and Greenland limit land-ice contributions to sea level rise by resisting the flow of grounded ice. Melting at the surface and base of ice shelves can lead to destabilisation by promoting thinning and fracturing. Basal melting often results in channelised features that manifest as surface topography due to buoyancy. The assumption of hydrostatic flotation commonly underlies estimates of basal melting rates. However, numerical simulations and ice-penetrating radar data have shown that narrow topographic features do not necessarily satisfy the local flotation condition. Here, we introduce a linearised model for ice-shelf topographic response to basal melting perturbations to quantify deviations from hydrostatic flotation and the stability of topography. While hydrostatic flotation is the dominant behaviour at wavelengths greater than the ice thickness, ice elevation anomalies diminish relative to the perfect flotation condition at smaller wavelengths. The linearised analysis shows that steady solutions are stable. However, we do not consider physical effects such as fracturing, which could lead to instability. We find a Green’s function for one-dimensional steady-state solutions in the absence of background advection. We validate the linearised analysis by comparing numerical solutions to a nonlinear ice-flow model with steady-state solutions obtained via the Green’s function.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Linear analysis of ice-shelf topography response to basal melting and freezing

Stubblefield¹,

Meyer²,

Wearing³

2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Several nonlinear effects not considered in our analysis may also influence the evolution of melt-generated ice shelf topography. For example, ice deformation regimes such as proximity to the grounding line, varying ice-shelf geometry, fracture, buttressing, or viscoelasticity may produce different non-hydrostatic effects or stability criteria relative to the idealized shelves considered here [4,22,45,65]. Quantifying the influence of these more complex stress regimes on channel evolution would be valuable.…”

Section: Discussionmentioning

confidence: 99%

“…Although melting dominates the basal mass balance of most Antarctic ice shelves [16], altimetry, ice-penetrating radar and numerical models have shown that many ice shelves have regions where water is freezing to the base [17][18][19][20][21][22]. Borehole drilling has shown that thick units of frozen-on marine ice exist beneath the Amery Ice Shelf [23][24][25] and the Ronne-Filchner Ice Shelf [26,27].…”

Section: Introductionmentioning

confidence: 99%

Linear analysis of ice-shelf topography response to basal melting and freezing

Stubblefield,

Wearing,

Meyer

2023

Proc. R. Soc. A.

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Floating ice shelves in Antarctica and Greenland limit land-ice contributions to sea-level rise by resisting the flow of grounded ice. Melting at the surface and base of ice shelves can lead to destabilization by promoting thinning and fracturing. Basal melting often results in channelized features that manifest as surface topography due to buoyancy. The assumption of hydrostatic flotation commonly underlies estimates of basal melting rates. However, numerical simulations and ice-penetrating radar data have shown that narrow topographic features do not necessarily satisfy the local flotation condition. Here, we introduce a linearized model for ice-shelf topographic response to basal melting perturbations to quantify deviations from hydrostatic flotation and the stability of topography. While hydrostatic flotation is the dominant behaviour at wavelengths greater than the ice thickness, ice elevation can deviate from the perfect flotation condition at smaller wavelengths. The linearized analysis shows that channelized features can be stable when the time scale of extensional thinning is small relative to the time scale of viscous flow towards the channel. When extension is non-negligible, channels can break through the ice column. We validate the linearized analysis by comparing numerical solutions to a nonlinear ice-flow model with steady-state solutions obtained via a Green’s function.

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“…Fresh water is delivered to the ocean from the upstream grounded ice through this region; where fresh water meets the relatively warm, saline ocean water the lower density fresh water rises, permitting the warm water to intrude upstream of the grounding line [8]. There is growing evidence of warm water intrusions upstream of grounding lines from diverse sources including surface observations [28,29], satellite data [6,30], and ice shelf basal features [31].…”

mentioning

confidence: 99%

Tipping point behaviour of submarine melting in ice-sheet grounding zones

Hewitt

Bradley

2023

Preprint

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Marine ice sheets are highly sensitive to submarine melting in their grounding zones, where they transition between grounded and floating ice. Recently published studies of the complex hydrography of grounding zones suggest that warm ocean water can intrude large distances beneath the ice sheet, with dramatic consequences for ice dynamics. Here, we develop a model to capture the feedback between intruded ocean water, the melting it induces, and the resulting changes in ice geometry. We reveal a sensitive dependence of the grounding zone dynamics on this feedback: as the grounding zone widens in response to melting, both temperature and flow velocity in the region increase, further enhancing melting. Intriguingly, we find that increases in ocean temperature can lead to a tipping point being passed, beyond which ocean water intrudes in an unbounded manner beneath the ice sheet, via a process of runaway melting. This suggests a mechanism for dramatic changes in grounding zone behavior, which are not currently included in ice sheet models, and may enable them to reproduce previous high warm-period sea levels. We consider the susceptibility of present-day Antarctic grounding zones to this process, finding that both warm and cold water cavity ice shelves may be vulnerable. Our results point towards a stronger sensitivity of ice sheet melting, and thus higher sea level rise contribution in a warming climate, than has been previously understood.

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Melting and Refreezing in an Ice Shelf Basal Channel at the Grounding Line of the Kamb Ice Stream, West Antarctica

Cited by 7 publications

References 90 publications

Linear analysis of ice-shelf topography response to basal melting and freezing

Linear analysis of ice-shelf topography response to basal melting and freezing

Linear analysis of ice-shelf topography response to basal melting and freezing

Tipping point behaviour of submarine melting in ice-sheet grounding zones

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