Description and evaluation of the Community Ice Sheet Model (CISM) v2.1

Lipscomb, William H.; Price, Stephen; Hoffman, Matthew J.; Leguy, Gunter; Bennett, Andrew; Bradley, Sarah; Evans, Katherine J.; Fyke, Jeremy; Kennedy, Joseph H.; Perego, Mauro; Ranken, Doug; Sacks, William J.; Salinger, Andrew G.; Vargo, Lauren; Worley, Patrick H

doi:10.5194/gmd-12-387-2019

Cited by 105 publications

(132 citation statements)

References 73 publications

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“…In typical configurations (e.g., by default in CESM2 and CLM5 land‐only simulations), CLM5 computes ice sheet surface mass balance, but ice sheets do not evolve. CLM5 can also be coupled bidirectionally to CISM2.1 (Lipscomb et al, ) and thereby simulate an evolving Greenland ice sheet. The introduction of the capability to adjust land unit weights during a simulation (section ) means that a glacier can incept, grow, shrink, or disappear during a simulation when two‐way coupling between the land and ice sheet model is active.…”

Section: Model Descriptionmentioning

confidence: 99%

The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

Lawrence¹,

Fisher²,

Koven³

et al. 2019

J Adv Model Earth Syst

Self Cite

945

972

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The Community Land Model (CLM) is the land component of the Community Earth System Model (CESM) and is used in several global and regional modeling systems. In this paper, we introduce model developments included in CLM version 5 (CLM5), which is the default land component for CESM2. We assess an ensemble of simulations, including prescribed and prognostic vegetation state, multiple forcing data sets, and CLM4, CLM4.5, and CLM5, against a range of metrics including from the International Land Model Benchmarking (ILAMBv2) package. CLM5 includes new and updated processes and Key Points: • Updated Community Land Model has more hydrological and ecological process fidelity and more comprehensive representation of land management. • The model is systematically evaluated using International Land Model Benchmarking system and shows marked improvement over prior versions. parameterizations: (1) dynamic land units, (2) updated parameterizations and structure for hydrology and snow (spatially explicit soil depth, dry surface layer, revised groundwater scheme, revised canopy interception and canopy snow processes, updated fresh snow density, simple firn model, and Model for Scale Adaptive River Transport), (3) plant hydraulics and hydraulic redistribution, (4) revised nitrogen cycling (flexible leaf stoichiometry, leaf N optimization for photosynthesis, and carbon costs for plant nitrogen uptake), (5) global crop model with six crop types and time-evolving irrigated areas and fertilization rates, (6) updated urban building energy, (7) carbon isotopes, and (8) updated stomatal physiology. New optional features include demographically structured dynamic vegetation model (Functionally Assembled Terrestrial Ecosystem Simulator), ozone damage to plants, and fire trace gas emissions coupling to the atmosphere. Conclusive establishment of improvement or degradation of individual variables or metrics is challenged by forcing uncertainty, parametric uncertainty, and model structural complexity, but the multivariate metrics presented here suggest a general broad improvement from CLM4 to CLM5. Plain Language Summary The Community Land Model (CLM) is the land component of the widely used Community Earth System Model (CESM). Here, we introduce model developments included in CLM version 5 (CLM5), the default land component for CESM2 which will be used for the Coupled Model Intercomparison Project (CMIP6). CLM5 includes many new and updated processes including (1) hydrology and snow features such as spatially explicit soil depth, canopy snow processes, a simple firn model, and a more mechanistic river model, (2) plant hydraulics and hydraulic redistribution, (3) revised nitrogen cycling with flexible leaf stoichiometry, leaf N optimization for photosynthesis, and carbon costs for plant nitrogen uptake, (4) expansion to six crop types (global) and time-evolving irrigated areas and fertilization rates, (5) improved urban building energy model, and (6) carbon isotopes. New optional features include a demographically structured dynamic vegetat...

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Section: Model Descriptionmentioning

confidence: 99%

The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

Lawrence¹,

Fisher²,

Koven³

et al. 2019

J Adv Model Earth Syst

Self Cite

945

972

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show abstract

“…CESM1 used the Glimmer Community Ice Sheet Model (a serial code with simplified shallow-ice dynamics) and was limited to one-way coupling; the ice sheet could respond dynamically to surface mass balance (SMB) forcing from the land model, but land surface topography and surface types could not evolve. The ice sheet component of CESM2 is the Community Ice Sheet Model Version 2.1 (CISM2.1; Lipscomb et al, 2019), a state-of-the-art parallel model with higher-order velocity solvers (valid for fast-flowing ice streams and ice shelves) and improved treatments of basal sliding, iceberg calving, and other physical processes. The simulations in this manuscript assume fixed ice sheets, but CESM2 also supports two-way coupling between the Greenland ice sheet and the land and atmosphere models.…”

Section: Land Icementioning

confidence: 99%

The Community Earth System Model Version 2 (CESM2)

Danabasoglu

Lamarque

Bacmeister

et al. 2020

J Adv Model Earth Syst

1,312

913

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An overview of the Community Earth System Model Version 2 (CESM2) is provided, including a discussion of the challenges encountered during its development and how they were addressed. In addition, an evaluation of a pair of CESM2 long preindustrial control and historical ensemble simulations is presented. These simulations were performed using the nominal 1° horizontal resolution configuration of the coupled model with both the “low‐top” (40 km, with limited chemistry) and “high‐top” (130 km, with comprehensive chemistry) versions of the atmospheric component. CESM2 contains many substantial science and infrastructure improvements and new capabilities since its previous major release, CESM1, resulting in improved historical simulations in comparison to CESM1 and available observations. These include major reductions in low‐latitude precipitation and shortwave cloud forcing biases; better representation of the Madden‐Julian Oscillation; better El Niño‐Southern Oscillation‐related teleconnections; and a global land carbon accumulation trend that agrees well with observationally based estimates. Most tropospheric and surface features of the low‐ and high‐top simulations are very similar to each other, so these improvements are present in both configurations. CESM2 has an equilibrium climate sensitivity of 5.1–5.3 °C, larger than in CESM1, primarily due to a combination of relatively small changes to cloud microphysics and boundary layer parameters. In contrast, CESM2's transient climate response of 1.9–2.0 °C is comparable to that of CESM1. The model outputs from these and many other simulations are available to the research community, and they represent CESM2's contributions to the Coupled Model Intercomparison Project Phase 6.

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“…Grounding line parameterizations (GLPs), which give a smooth transition in basal shear 25 stress across the transition zone, have been shown to improve numerical accuracy in models with relatively coarse grids (e.g., Gladstone et al, 2010;Leguy et al, 2014;Seroussi et al, 2014). CISM has a GLP that was not used for the Greenland simulations in Lipscomb et al (2019), but is used for Antarctic simulations and is described in Appendix A.…”

Section: The Community Ice Sheet Modelmentioning

confidence: 99%

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

Lipscomb

Leguy

Jourdain

et al. 2020

Preprint

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Abstract. The future retreat rate for marine-based regions of the Antarctic Ice Sheet is one of the largest uncertainties in sea-level projections. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) aims to improve projections and quantify uncertainties by running an ensemble of ice sheet models with atmosphere and ocean forcing derived from global climate models. Here, ISMIP6 projections of ocean-forced Antarctic Ice Sheet evolution are illustrated using the Community Ice Sheet Model (CISM). Using multiple combinations of sub-ice-shelf melt parameterizations and calibrations, CISM is spun up to steady state over many millennia. During the spin-up, basal friction parameters and basin-scale thermal forcing corrections are adjusted to nudge the ice thickness toward observed values. The model is then run forward for 500 years, applying ocean thermal forcing anomalies from six climate models. In all simulations, the ocean forcing triggers long-term retreat of the West Antarctic Ice Sheet, including the Amundsen, Filchner-Ronne, and Ross Basins. Mass loss accelerates late in the 21st century and rises steadily over the next several centuries without leveling off. The resulting ocean-forced SLR at year 2500 varies from about 10 cm to nearly 2 m, depending on the melt scheme and model forcing. Relatively little ice loss is simulated in East Antarctica. Large uncertainties remain, as a result of parameterized basal melt rates, missing ocean and ice sheet physics, and the lack of ice–ocean coupling.

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Description and evaluation of the Community Ice Sheet Model (CISM) v2.1

Cited by 105 publications

References 73 publications

The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

The Community Land Model Version 5: Description of New Features, Benchmarking, and Impact of Forcing Uncertainty

The Community Earth System Model Version 2 (CESM2)

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

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