Asynchronous Coupling of Ice-Sheet and Atmospheric Forcing Models

Pollard, David; Muszynski, Isabelle; Schneider, Stephen H.; Thompson, Starley L.

doi:10.1017/s0260305500008685

Cited by 10 publications

(4 citation statements)

References 17 publications

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“…Thus step (1) would be repeated at intervals of several thousand years with the GCM's prescribed ice-sheet mask and surface topography updated to reflect the current state of the dynamic ice sheets and bedrock. (Pollard and others, 1990). However in the application below we have essentially performed only the first step in such an integration, and have stopped the simulation after 10 000 years without re-running the GCM.…”

Section: Description Of Models and Coupling Strategymentioning

confidence: 99%

Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

Pollard

Thompson

1997

Ann. Glaciol.

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Most dynamic ice-sheet studies currently use either empirically based parameterizations or simple energy-balance climate models for the surface mass-balance forcing. If three-dimensional global climate models (GCMs) could be used instead, they would greatly improve the potential realism of coupled climate ice-sheet simulations. However, there are two serious problems in simulating realistic mass balances on ice sheets from GCM simulations: (i) dynamic ice-sheet models and the underlying bedrock topography need horizontal resolution of 50–100 km or less, but the finest practical resolution of atmospheric GCMs is currently ˜250 km, and (ii) GCM surface physics usually neglects the local refreezing of meltwater on ice sheets.Two techniques are described that address these problems: an elevation correction applied to the atmospheric GCM fields interpolated to the ice-sheet grid, and a refreezing correction involving the annual totals of snowfall, rainfall and local melt at each grid-point. As an example of their use, we have used the GENESIS version 2 GCM at 3.75° × 3.75° resolution to simulate the climate at the end of the last interglaciation at ˜116 000 years ago. The atmospheric climate is then used to drive a standard two-dimensional dynamic ice-sheet model for 10 000 years on a 0.5° × 0.5° grid spanning northern North America. The model successfully predicts ice-sheet initiation over the Baffin Island highlands and the Canadian Archipelago, but at a slower rate than observed. A large ice sheet nucleates and grows rapidly over the northwestern Rockies, in conflict with geologic evidence. Possible reasons for these discrepancies are discussed.

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Section: Description Of Models and Coupling Strategymentioning

confidence: 99%

Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

Pollard

Thompson

1997

Ann. Glaciol.

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“…Since much interest of coupled Earth system/ice sheet simulations lies in centennial or millennial timescales, techniques to reduce costs for long simulations are needed. One possible approach is the development of robust, flexible, modular coupling schemes, using asynchronous or “periodic synchronous” coupling (Mikolajewicz et al., 2007 ; Pollard et al., 1990 ; Ridley et al., 2005 ; Ziemen et al., 2014 ). A similar approach was adopted to generate the initial conditions for the simulations in this study (Lofverstrom et al., 2020 ).…”

Section: Discussionmentioning

confidence: 99%

Description and Demonstration of the Coupled Community Earth System Model v2 – Community Ice Sheet Model v2 (CESM2‐CISM2)

Muntjewerf

Sacks

Löfverström

et al. 2021

J Adv Model Earth Syst

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Earth system/ice‐sheet coupling is an area of recent, major Earth System Model (ESM) development. This work occurs at the intersection of glaciology and climate science and is motivated by a need for robust projections of sea‐level rise. The Community Ice Sheet Model version 2 (CISM2) is the newest component model of the Community Earth System Model version 2 (CESM2). This study describes the coupling and novel capabilities of the model, including: (1) an advanced energy‐balance‐based surface mass balance calculation in the land component with downscaling via elevation classes; (2) a closed freshwater budget from ice sheet to the ocean from surface runoff, basal melting, and ice discharge; (3) dynamic land surface types; and (4) dynamic atmospheric topography. The Earth system/ice‐sheet coupling is demonstrated in a simulation with an evolving Greenland Ice Sheet (GrIS) under an idealized high CO2 scenario. The model simulates a large expansion of ablation areas (where surface ablation exceeds snow accumulation) and a large increase in surface runoff. This results in an elevated freshwater flux to the ocean, as well as thinning of the ice sheet and area retreat. These GrIS changes result in reduced Greenland surface albedo, changes in the sign and magnitude of sensible and latent heat fluxes, and modified surface roughness and overall ice sheet topography. Representation of these couplings between climate and ice sheets is key for the simulation of ice and climate interactions.

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“…The most recently computed mass balance is used to drive the ice sheet model through the next several-thousand-year asynchronous period. Each snapshot requires a few decades of GCM integration to spin up the upper ocean and to average out interannual variability (Pollard et al 1990). This technique was used by Charbit et al (2002) to simulate the last Northern Hemispheric deglaciation since 21 ka, and by Horton and Poulsen (2009) in Permo-Carboniferous ice-age experiments.…”

Section: Basic Asynchronous With Gcms and Emicsmentioning

confidence: 99%

A retrospective look at coupled ice sheet–climate modeling

Pollard

2010

Climatic Change

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Since its inception, numerical climate modeling has evolved along with available computer power. Limitations in computer power quickly led to distinct types of models, with relatively simple models capable of long integrations, versus complex models suitable for short-duration detailed snapshots. Recognizing these computing limitations, strategies to combine and enhance knowledge from the different model types were conceived, and Schneider and Dickinson (1974) were early proponents of interactive "hierarchies" of models. In that framework, numerical climate models of different complexities, ranging from energy balance models (EBMs) for longterm simulations, through zonal statistical-dynamic models and nowadays, Earth models of intermediate complexity (EMICs), to general circulation (or global climate) models (GCMs) for short-term weather details, are used in combination with each other. For instance, the GCM is used to determine key sensitivities (to orbital perturbations, for example), and then the EBM is tuned to have the same sensitivities. Knowledge and experience at each level of the hierarchy is applied interactively at other levels. Climate-model hierarchies have also been discussed by Henderson-Sellers and McGuffie (1987), Claussen et al. (2002) and Bartlein and Hostetler (2004), with Claussen et al. (2002) distinguishing between integration of components vs. detail of description, and proposing the term "spectrum" to avoid any suggestion that one hierarchical level is better than another (Fig. 1).This paper briefly surveys how these ideas have found form over the last several decades, in the area of coupled ice sheet-climate modeling. To some extent the original concept of hierarchies has been realized, but mostly it has been adapted in different ways than originally envisioned, driven by the need to address the very

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Asynchronous Coupling of Ice-Sheet and Atmospheric Forcing Models

Cited by 10 publications

References 17 publications

Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

Driving a high-resolution dynamic ice-sheet model with GCM climate: ice-sheet initiation at 116 000 BP

Description and Demonstration of the Coupled Community Earth System Model v2 – Community Ice Sheet Model v2 (CESM2‐CISM2)

A retrospective look at coupled ice sheet–climate modeling

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