Diagnosing the sensitivity of grounding-line flux to changes in sub-ice-shelf melting

Zhang, T.; Price, Stephen; Hoffman, Matthew J.; Perego, Mauro; Asay‐Davis, Xylar

doi:10.5194/tc-14-3407-2020

Cited by 11 publications

(18 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This definition is in line with the original view of buttressing as the backstresses produced by an ice shelf that are felt at the grounding line (Thomas, 1979). This is the approach used in the work of Reese et al (2018) and Zhang et al (2020), who focus on the GLF response to ice-shelf perturbations. We find that the regions with the largest 'buttressing flux response number' (Reese et al, 2018) correspond to the regions providing the majority of the buttressing in our calving experiments.…”

Section: Thinning Experimentsmentioning

confidence: 56%

“…This allowed them to determine the regions in the ice shelf where a perturbation in ice thickness would produce the largest response in GLF, and they also demonstrated that small changes in ice-shelf thickness could impact the GLF hundreds of kilometres away. Finally, Zhang et al (2020) explored the correlation between locally derived buttressing numbers in the ice shelf, and changes in GLF due to small perturbations in ice-shelf thickness at the same locations. They found that for a real-world ice shelf (the LCIS) there was no relationship between these two measures, and that locally derived buttressing numbers are not predictors for the impact of perturbations in ice-shelf geometry on GLF.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The impact of recent and future calving events on the Larsen C ice shelf

Mitcham

Gudmundsson

Bamber

2021

Preprint

View full text Add to dashboard Cite

Abstract. The Antarctic Peninsula has seen rapid and widespread changes in the extent of its ice shelves in recent decades, including the collapse of the Larsen A and B ice shelves in 1995 and 2002, respectively. In 2017 the Larsen C ice shelf (LCIS) lost around 10 % of its area by calving one of the largest icebergs ever recorded (A68). This has raised questions about the structural integrity of the shelf and the impact of any changes in its extent on the flow of its tributary glaciers. In this work, we used an ice flow model to study the instantaneous impact of changes in the thickness and extent of the LCIS on ice dynamics, and in particular on changes in the grounding line flux (GLF). We initialised the model to a pre-A68 calving state, and first replicated the calving of the A68 iceberg. We found that there was a limited impact on upstream flow – with speeds increasing by less than 10 % across almost all of the shelf – and a 0.5 % increase in GLF. This result is supported by observations of ice velocity made before and after the calving event. We then perturbed the ice-shelf geometry through idealised calving and thinning experiments of increasing magnitude. We found that significant changes to the geometry of the ice shelf, through both calving and thinning, resulted in limited changes in GLF. For example, to produce a doubling of GLF from calving, the new calving front needed to be moved to 5 km from the grounding line, removing almost the entire ice shelf. For thinning, over 200 m of the ice-shelf thickness had to be removed across the whole shelf to produce a doubling of GLF. Calculating the increase in GLF (607 %) after removing the entire ice shelf allowed us to quantify the total amount of buttressing provided by the LCIS. From this, we identified that the region of the ice shelf in the first 5 km downstream of the grounding line provided over 80 % of the buttressing capacity of the shelf. This is due to the large resistive stresses generated in the narrow, local embayments downstream of the largest tributary glaciers.

show abstract

Section: Thinning Experimentsmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

The impact of recent and future calving events on the Larsen C ice shelf

Mitcham

Gudmundsson

Bamber

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…This definition is in line with the original view of buttressing as the back stresses produced by an ice shelf that are felt at the grounding line (Thomas, 1979). This is the approach used in the work of Reese et al (2018), Gudmundsson et al (2019) and Zhang et al (2020), who focus on the GLF response to ice-shelf perturbations. We find that the regions with the largest "buttressing flux response number" (Reese In panels (a)-(c) there is a small speed decrease (typically < 10 m a −1 ) at a few computational nodes that is not visible when plotted, and therefore the colour scale has been truncated at zero for clarity.…”

Section: Calving Experiments and Ice-shelf Buttressingmentioning

confidence: 56%

“…The previous work of Reese et al (2018) and Zhang et al (2020) measured the response in GLF to small perturbations in ice-shelf geometry, but by removing the entire ice shelf and calculating the instantaneous response in GLF we are able to quantify the total amount of buttressing that the LCIS provides. This allowed us to examine what proportion of the total buttressing capacity is provided by different regions in the ice shelf.…”

Section: Calving Experiments and Ice-shelf Buttressingmentioning

confidence: 99%

“…In their experiments, they were able to map, or "fingerprint", the instantaneous ice velocity response and the reduction in buttressing due to the cumulative observed ice-shelf thinning from 1994 to 2017. Zhang et al (2020) explored the correlation between locally derived buttressing numbers in the ice shelf and changes in GLF due to small perturbations in iceshelf thickness at the same locations. They found that for a real-world ice shelf (the LCIS) there was no relationship between these two measures and that locally derived buttressing numbers are not predictors for the impact of perturbations in ice-shelf geometry on GLF.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The instantaneous impact of calving and thinning on the Larsen C Ice Shelf

2022

View full text Add to dashboard Cite

Abstract. The Antarctic Peninsula has seen rapid and widespread changes in the extent of its ice shelves in recent decades, including the collapse of the Larsen A and B ice shelves in 1995 and 2002, respectively. In 2017 the Larsen C Ice Shelf (LCIS) lost around 10 % of its area by calving one of the largest icebergs ever recorded (A68). This has raised questions about the structural integrity of the shelf and the impact of any changes in its extent on the flow of its tributary glaciers. In this work, we used an ice flow model to study the instantaneous impact of changes in the thickness and extent of the LCIS on ice dynamics and in particular on changes in the grounding line flux (GLF). We initialised the model to a pre-A68 calving state and first replicated the calving of the A68 iceberg. We found that there was a limited instantaneous impact on upstream flow – with speeds increasing by less than 10 % across almost all of the shelf – and a 0.28 % increase in GLF. This result is supported by observations of ice velocity made before and after the calving event. We then perturbed the ice-shelf geometry through a series of instantaneous, idealised calving and thinning experiments of increasing magnitude. We found that significant changes to the geometry of the ice shelf, through both calving and thinning, resulted in limited instantaneous changes in GLF. For example, to produce a doubling of GLF from calving, the new calving front needed to be moved to 5 km from the grounding line, removing almost the entire ice shelf. For thinning, over 200 m of the ice-shelf thickness had to be removed across the whole shelf to produce a doubling of GLF. Calculating the instantaneous increase in GLF (607 %) after removing the entire ice shelf allowed us to quantify the total amount of buttressing provided by the LCIS. From this, we identified that the region of the ice shelf in the first 5 km downstream of the grounding line provided over 80 % of the buttressing capacity of the shelf. This is due to the large resistive stresses generated in the narrow, local embayments downstream of the largest tributary glaciers.

show abstract

Effects of calving and submarine melting on steady states and stability of buttressed marine ice sheets

Haseloff

Sergienko

2022

J. Glaciol.

View full text Add to dashboard Cite

Mass loss from ice shelves is a strong control on grounding-line dynamics. Here we investigate how calving and submarine melt parameterizations affect steady-state grounding-line positions and their stability. Our results indicate that different calving laws with the same melt parameterization result in more diverse steady-state ice-sheet configurations than different melt parameterizations with the same calving law. We show that the backstress at the grounding line depends on the integrated ice-shelf mass flux. Consequently, ice shelves are most sensitive to high melt rates in the vicinity of their grounding lines. For the same shelf-averaged melt rates, different melt parameterizations can lead to very different ice-shelf configurations and grounding-line positions. If the melt rate depends on the slope of the ice-shelf draft, then the positive feedback between increased melting and steepening of the slope can lead to singular melt rates at the ice-shelf front, producing an apparent lower limit of the shelf front thickness as the ice thickness vanishes over a small boundary layer. Our results illustrate that the evolution of marine ice sheets is highly dependent on ice-shelf mass loss mechanisms, and that existing parameterizations can lead to a wide range of modelled grounding-line behaviours.

show abstract

Diagnosing the sensitivity of grounding-line flux to changes in sub-ice-shelf melting

Cited by 11 publications

References 45 publications

The impact of recent and future calving events on the Larsen C ice shelf

The impact of recent and future calving events on the Larsen C ice shelf

The instantaneous impact of calving and thinning on the Larsen C Ice Shelf

Effects of calving and submarine melting on steady states and stability of buttressed marine ice sheets

Contact Info

Product

Resources

About