ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model

Lipscomb, William H.; Leguy, Gunter; Jourdain, Nicolas C.; Asay‐Davis, Xylar; Seroussi, Hélène; Nowicki, Sophie

doi:10.5194/tc-2019-334

Cited by 5 publications

(17 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For both the MISMIP3d and the sub-ice-shelf melt experiments, and for any choice of p or grid resolution, the results with the DIVA solver are close to those with the more expensive BP solver, consistent with CISM simulations of Greenland and Antarctica (Lipscomb et al, 2019(Lipscomb et al, , 2020. The SSA solver, which is valid when basal stresses are low enough that there is little vertical shear, gives results similar to DIVA and BP in the MISMIP+ framework, but overestimates the ice viscosity for MISMIP3d, leading to greater grounding-line advance.…”

Section: Experiments 2: High Basal Melt Ratesupporting

confidence: 60%

“…In regions where the seabed deepens upstream of the grounding line, this retreat can be self-reinforcing (Schoof, 2007a). Research is ongoing (Seroussi et al, 2020;Rückamp et al, 2020;Lipscomb et al, 2020) to better understand and model the physical processes responsible for marine ice-sheet behavior, in order to better forecast future mass loss and sea-level rise.…”

Section: Introductionmentioning

confidence: 99%

“…CISM has been coupled to the Community Earth System Model (CESM; Hurrell et al, 2013;Danabasoglu et al, 2020) and used in interactive ice sheet-climate simulations with a dynamic Greenland Ice Sheet (Muntjewerf et al, 2020a, b). Recently, CISM has been used for standalone Antarctic Ice Sheet simulations (Seroussi et al, 2019(Seroussi et al, , 2020Levermann et al, 2019;Lipscomb et al, 2020), and work is underway to extend CESM-CISM coupling to Antarctica and other marine-based ice sheets. Antarctic applications have motivated us to test the accuracy and robustness of model numerics related to grounding-line dynamics.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Marine ice-sheet experiments with the Community Ice Sheet Model

Leguy¹,

Lipscomb²,

Asay‐Davis³

2020

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We study the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice SheetModel (CISM). In the framework of the Marine Ice Sheet Model Intercomparison Project 3d (MISMIP3d), we show that a depth-integrated, higher-order solver gives results similar to a 3D (Blatter-Pattyn) solver. We confirm that using a grounding-line parameterization to approximate stresses in the grounding zone leads to accurate representation of ice sheet flow with a resolution of ∼2 km, as opposed to ∼0.5 km without the parameterization. In the MISMIP+ experimental framework, we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In both experimental frameworks, ice flow is sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate, and ∼1 km (arguably 2 km) when the connectivity is strong.

show abstract

Section: Experiments 2: High Basal Melt Ratesupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Marine ice-sheet experiments with the Community Ice Sheet Model

Leguy¹,

Lipscomb²,

Asay‐Davis³

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The viscosity is vertically averaged, and basal friction is cast in terms of the depth-averaged velocity. This solver has been used by continental-scale models to investigate dynamics and interactions with climate for the Greenland and Antarctic ice sheets (Arthern et al, 2015;Arthern and Williams, 2017;Lipscomb et al, 2019Lipscomb et al, , 2021.…”

Section: Introductionmentioning

confidence: 99%

A comparison of the stability and performance of depth-integrated ice-dynamics solvers

2022

Self Cite

View full text Add to dashboard Cite

Abstract. In the last decade, the number of ice-sheet models has increased substantially, in line with the growth of the glaciological community. These models use solvers based on different approximations of ice dynamics. In particular, several depth-integrated dynamics solvers have emerged as fast solvers capable of resolving the relevant physics of ice sheets at the continental scale. However, the numerical stability of these schemes has not been studied systematically to evaluate their effectiveness in practice. Here we focus on three such solvers, the so-called Hybrid, L1L2-SIA and DIVA solvers, as well as the well-known SIA and SSA solvers as boundary cases. We investigate the numerical stability of these solvers as a function of grid resolution and the state of the ice sheet for an explicit time discretization scheme of the mass conservation step. Under simplified conditions with constant viscosity, the maximum stable time step of the Hybrid solver, like the SIA solver, has a quadratic dependence on grid resolution. In contrast, the DIVA solver has a maximum time step that is independent of resolution as the grid becomes increasingly refined, like the SSA solver. A simple 1D implementation of the L1L2-SIA solver indicates that it should behave similarly, but in practice, the complexity of its implementation appears to restrict its stability. In realistic simulations of the Greenland Ice Sheet with a nonlinear rheology, the DIVA and SSA solvers maintain superior numerical stability, while the SIA, Hybrid and L1L2-SIA solvers show markedly poorer performance. At a grid resolution of Δx=4 km, the DIVA solver runs approximately 20 times faster than the Hybrid and L1L2-SIA solvers as a result of a larger stable time step. Our analysis shows that as resolution increases, the ice-dynamics solver can act as a bottleneck to model performance. The DIVA solver emerges as a clear outlier in terms of both model performance and its representation of the ice-flow physics itself.

show abstract

“…In their extended ISMIP6 study, Lipscomb et al (2021) found two parameters to be especially important to the sensitivity of the ice sheet. The first, γ 0 , is a constant in the TF parameterization that scales melt rates for a given ocean TF.…”

Section: Introductionmentioning

confidence: 99%

Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Berdahl

Leguy

Lipscomb

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Multi-meter sea level rise (SLR) is thought to be possible within a century or two, with most of the uncertainty originating from the Antarctic land ice contribution. One source of uncertainty relates to the ice sheet model initialization. Since ice sheets have a long response time (compared to other Earth system components such as the atmosphere), ice sheet model initialization methods can have significant impacts on how the ice sheet responds to future forcings. To assess this, we generated 25 different ice sheet spin-ups, using the Community Ice Sheet Model (CISM) at 4 km resolution. During each spin-up we varied two key parameters known to impact the sensitivity of the ice sheet to future forcing: One related to the sensitivity of the ice-shelf melt rate to ocean thermal forcing, and the other related to the basal friction. The spin-ups all nudge toward observed thickness and enforce a no-advance calving criterion, such that all final spun-up states resemble observations but differ in their melt and friction parameter settings. Each spin-up was then forced with future ocean thermal forcings from 13 different CMIP6 models under the SSP5-8.5 emissions scenario, and modern climatological surface mass balance data. Our results show that the effects of the ice sheet and ocean parameter settings used during the spin-up are capable of impacting multi-century future SLR predictions by as much as 2 m. By the end of this century, the effects of these choices are more modest, but still significant, with differences of up to 0.2 m of SLR. We have identified a combined ocean and ice parameter space that leads to widespread mass loss (low friction & high melt rate sensitivity). To explore temperature thresholds, we also ran a synthetically-forced CISM ensemble that is focused on the Amundsen region only. We find that given certain ocean and ice parameter choices, Amundsen mass loss can be triggered with thermal forcing anomalies between 1.5 and 2 °C. Our results emphasize the critical importance of considering ice sheet/ocean parameter choices during spin-up for sea level rise predictions.

show abstract

ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model

Cited by 5 publications

References 36 publications

Marine ice-sheet experiments with the Community Ice Sheet Model

Marine ice-sheet experiments with the Community Ice Sheet Model

A comparison of the stability and performance of depth-integrated ice-dynamics solvers

Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Contact Info

Product

Resources

About