Benchmarking the vertically integrated ice-sheet model IMAU-ICE (version 2.0)

Berends, Constantijn J.; Goelzer, Heiko; Reerink, Thomas; Stap, Lennert B.; Wal, R. S. W. van de

doi:10.5194/gmd-15-5667-2022

Cited by 11 publications

(15 citation statements)

References 74 publications

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“…This makes it similar to the more commonly used hybrid shallow ice/shallow shelf approximation (SIA/SSA) (Bueler and Brown, 2009), but more mathematically consistent. Its solution remains close to the full-Stokes solution at much smaller horizontal scales, down from ~20 km for the hybrid SIA/SSA to ~5 km for the DIVA (Goldberg, 2011; Lipscomb and others, 2019; Berends and others, 2022). The hybrid SIA/SSA stress balance can still optionally be used instead of the DIVA.…”

Section: Model Descriptionmentioning

confidence: 74%

“…IMAU-ICE is a vertically averaged ice-dynamical model (Berends and others, 2022). It solves the depth-integrated viscosity approximation (DIVA; Goldberg, 2011) to the full-Stokes equations on a square grid, using finite differences for the discretisation.…”

Section: Model Descriptionmentioning

confidence: 99%

“…The hybrid SIA/SSA stress balance can still optionally be used instead of the DIVA. Basal stress near the grounding line is scaled with the sub-grid grounded fraction, following the approach adopted by the Parallel Ice-Sheet Model (PISM; Feldmann and others, 2014) and the Community Ice-Sheet Model (CISM; Leguy and others, 2021), resulting in a grounding-line hysteresis after the forced advance/retreat of the Marine Ice-Sheet Model Intercomparison Project (MISMIP) experiment (Pattyn and others, 2012) that is smaller than the grid resolution (Berends and others, 2022). The model is thermomechanically coupled, with the ice flow factor depending on the englacial temperature according to an Arrhenius relation (Huybrechts, 1992).…”

Section: Model Descriptionmentioning

confidence: 99%

“…Such a state would require the use of an inversion, either for ocean temperatures or directly for melt rates as is done e.g. in Berends and others (2022). In future work, we will design a more sophisticated spin-up including spatially variable basal roughness, which will then also be used for more realistic projections of the Antarctic ice sheet.…”

Section: Realistic Antarctic Geometry Experimentsmentioning

confidence: 99%

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Strong impact of sub-shelf melt parameterisation on ice-sheet retreat in idealised and realistic Antarctic topography

2023

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Future projections of sea-level rise under strong warming scenarios are dominated by mass loss in the marine-grounded sectors of West Antarctica, where thinning shelves as a result of warming oceans can lead to reduced buttressing. This consequently leads to accelerated flow from the upstream grounded ice. However, the relation between warming oceans and increased melt rates under the shelves is very uncertain, especially when interactions with the changing shelf geometry are considered. Here, we compare six widely used, highly parameterised formulations relating sub-shelf melt to thermal forcing. We implemented them in an ice-sheet model, and applied the resulting set-up to an idealised-geometry setting, as well as to the Antarctic ice sheet. In our simulations, the differences in modelled ice-sheet evolution resulting from the choice of parameterisation, as well as the choice of numerical scheme used to apply sub-shelf melt near the grounding line, generally are larger than differences from ice-dynamical processes such as basal sliding, as well as uncertainties from the forcing scenario of the model providing the ocean forcing. This holds for the idealised-geometry experiments as well as for the experiments using a realistic Antarctic topography.

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Section: Model Descriptionmentioning

confidence: 74%

Section: Model Descriptionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Realistic Antarctic Geometry Experimentsmentioning

confidence: 99%

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Strong impact of sub-shelf melt parameterisation on ice-sheet retreat in idealised and realistic Antarctic topography

2023

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“…The other approach is the spin-up method (Winkelmann et al, 2011, Pollard and DeConto, 2012, Greve and Blatter, 2016, Quiquet et al, 2018, Lipscomb et al, 2019, Berends et al, 2021, Berends et al, 2022 consists of a run with paleoclimatic or preindustrial forcing during which the ice sheet can freely evolve. Uncertain parameter values can be tuned, to nudge variables like ice thickness and surface velocities toward present-day observed values.…”

mentioning

confidence: 99%

Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse

van den Akker,

Lipscomb,

Leguy

et al. 2024

Preprint

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Abstract. Observations of recent mass loss rates of the West Antarctic Ice Sheet (WAIS) raise concerns about its stability since a collapse would increase global sea levels by several meters. Future projections of these mass loss trends are often estimated using numerical ice sheet models. However, most current models display low skill in reproducing observed mass change rates accurately. Here, we develop a new initialization method that optimizes agreement not only with observations of ice thickness and surface velocity, but also with satellite-based estimates of mass change rates. Starting from this improved present-day state, we generate an ensemble of future projections of Antarctic mass change, covering uncertainties in model choices, parameter values and (observational) input data. Our ensemble displays a slow retreat over several centuries followed by a speed-up that lasts around 200 years. We find that for all ensemble members, the Thwaites and Pine Island glaciers collapse, even though the climate is held constant at present-day values. Our results imply that today’s mass loss rates are a precursor of the deglaciation of large parts of the WAIS, which would raise sea levels by at least a meter in the coming centuries, without additional climate forcing.

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Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse

Akker,

Lipscomb,

Leguy

et al. 2023

Preprint

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The observed mass loss from the West Antarctic Ice Sheet (WAIS) raises concerns about its stability1-4, since a collapse would raise global sea levels by several meters5. This mass loss is projected with ice sheet models that represent the present-day Antarctic ice sheet. We developed a new initialization method that optimizes agreement not only with ice thickness and surface velocity, but also with satellite-observed mass change rates. Starting from this initial state, we project future Antarctic mass changes while holding the ocean and atmospheric forcing constant at present-day values. We find that for a wide range of model settings, Thwaites Glacier and Pine Island Glacier collapse. The collapse is manifested by a slow retreat over several centuries followed by a significant speedup that lasts about 200 years. Our results imply that today’s mass loss rates are a precursor of the deglaciation of large parts of the WAIS, which would raise sea levels by at least a meter in the coming centuries, even without additional climate forcing.

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Benchmarking the vertically integrated ice-sheet model IMAU-ICE (version 2.0)

Cited by 11 publications

References 74 publications

Strong impact of sub-shelf melt parameterisation on ice-sheet retreat in idealised and realistic Antarctic topography

Strong impact of sub-shelf melt parameterisation on ice-sheet retreat in idealised and realistic Antarctic topography

Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse

Present-day mass loss rates are a precursor for West Antarctic Ice Sheet collapse

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