Participating Models
From Interactive System for Ice sheet Simulation
Since posting Table 1, additional description of the ice sheet models that took part in SeaRISE can be found in Bindschadler et al. (2013), Nowicki et al. (2013a) and Nowicki et al. (2013b). The models that completed the Greenland suite of experiments were: AIF, CISM2, IcIES, ISSM, Elmer/Ice, PISM, SICOPOLIS, and UMISM. The models that completed the Antarctic suite of experiments were: AIF, ISSM, PISM-PIK, PennState, SICOPOLIS, and UMISM.
Contents |
Table 1. Characteristics of Various Whole Ice-Sheet Models
Characteristics | Glimmer | CISM est. Q2 2009 | PISM link | MAINE | GLAM |
---|---|---|---|---|---|
Domain Flowline (1d or 2D); Plan view (2D or 3D) |
3D | 3D | 3D | map-plane | 3D |
SPACING Average grid spacing; Adaptive grid |
uniform grid > 10 km | uniform grid > 2.5 km | user-adjustable; model applications from 10 m grid to 80 km grid | can run whole ant at 20 km (70,000 nodes) with embed for higher res | uniform grid (resolution limited by desired model run-time) |
GRID Finite-difference; Finite-element; Eulerian/Lagrangian |
FD | FD + incremental remapping scheme | Eulerian; finite-difference | Finite Element quadrilaterals | FD |
FLOW APPROXIMATION Shallow ice; Shelfy-Stream; Higher-order; Full Stokes; other |
SIA | SIA + Price/Payne 1st Order + Pattyn/Johnson 1st Order | Hybrid model: SIA + SSA Bueler and Brown, 2009 | shallow ice | 1st – order SIA (e.g. Pattyn/Blatter models) |
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical + Polythermal of Greve | Thermomechanical + Polythermal (enthalpy formulation Aschwanden et al 2011) | Thermomechanical (1D columns with explicit vertical advection and diffusion, with horizontal advection as an additions “source” (negative heat)) | thermomechanical |
BASAL SLIDING Weertman sliding law; Coulomb plastic sliding law; Budd-type sliding law |
Proportional to driving stress and inverse water layer thickness | Flexible with linear and plasitc till being the most prominent | Coulomb plastic or Weertman | Weertman modified with a lubrication factor proportional to “amount” of water at the bed | linear-viscous sliding law (“B2” param.) w/ iteration for plastic bed sliding |
HYDROLOGY Surface, internal, basal water treatments |
Conservative steady state basal water routing | Surface and basal water treatments | basal meltwater model: controls bed strength | Basal melt water from thermo-calc used a source too diffusive-advective continuity model for basal water | local basal water production and storage; sub-model to link production rate to plastic till yield strength |
SURFACE MASS BALANCE Positive degree day; Surface energy balance; empirical method; other |
Positive degree day | Surface energy balance + downscaling of GCM data based upon elevation classes | Positive degree day or climate-model-specified. | Mean annual temp from latitudinal and elevation lapse rates, accumulation from MAT, ablation from PDD with lat-dependent amplitude around MAT | PDD scheme |
CALVING Calving "law"; calving mechanics |
Heuristic | Improved calving law based on stress/strain rates? | Fixed calving front or strain-rate-dependent calving law Winkelmann et al 2011 | Longitudinal extension at unbuttressed grounding line yields thinning rate at GL added to local mass balance, modified by "Weertman" parameter (1-no buttressing, 0-full buttressing) | Fixed calving front |
SPIN-UP/INITIALIZATION # glacial cycles; req'd initial fields |
One glacial cycle at minimum, preferable to do 2-3 | Concerns about performance make this a problem. HO physics may prevent long initialization periods. May have do some hybrid SIA/HO spin up, or find very powerful computers. | arbitrary number of glacial cycles. Surface elevation, bedrock elevation, geothermal flux | usually a glacial cycle, but 50Ka is usually enough | HO solver performance constraints make a simple steady-state spin up the most practical choice |
OTHER Explicit mass conservation |
Well documented problems (see EISMINT II) papers. We appear to be no worse than other comparable models. While this error relates to numerics, other errors arising in PDD schemes are unavoidable until a better (surface energy balance) scheme is used. | As before, again, placing some hope in better advection schemes. | yes, adaptive time-step | yes | Choice of solvers for mass conservation when using HO dynamics (e.g. Bueler explicit scheme, incremental remapping scheme) |
Grounding line migration | Major problem area. Currently I think it should be forced as part of the experimental setup. | As with before, but finer grids and incremental remapping scheme offer some hope.. | yes | GL determined by location surface drops below flotation height | Currently in 2d (x,z) plane only, using fine (~1km) grid spacing and grounding line interpolation ala Pattyn et al. (2006, JGR v.111) |
Publication describing the model (if available) | See PISM publications. |
Table 1 (Cont). Characteristics of Various Whole Ice-Sheet Models
Characteristics | PENN STATE | SICOPOLIS | Chicago | PENN STATE 2-D |
---|---|---|---|---|
Domain Flowline (1d or 2D); Plan view (2D or 3D) |
3D | 3D | flowline and plan view mode | flowline, 2-d |
SPACING Average grid spacing; Adaptive grid |
40 km, or nested 10 km to 5 km | ≥ 5 km for Greenland, ≥ 10 km for Antarctica; non-adaptive grid | variable resolution average, typically ~10 km | Depends on the simulation… for whole ice sheet, average ~10 km; adaptive |
GRID Finite-difference; Finite-element; Eulerian/Lagrangian |
finite difference | FD; Eulerian + sigma transformation in the vertical | finite difference in horizontal/spectral in vertical, semi-Lagrangian advection | Finite Element; Eulerian |
FLOW APPROXIMATION Shallow ice; Shelfy-Stream; Higher-order; Full Stokes; other |
Heuristic combination of shallow ice and shelfy stream | SIA (SSA for ice shelves currently under construction) | Other | SIA ready to go, Higher-order ready in isothermal mode |
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical + polythermal (front tracking by Greve) | Thermomechanical | SIA: thermomechanical; Higher-order: presently isothermal |
BASAL SLIDING Weertman sliding law; Coulomb plastic sliding law; Budd-type sliding law | Weertman sliding law | Weertman, adjustable exponents, optional sub-melt sliding | adjustable, tested with Weertman, Budd-type and Mohr-Coulomb | SIA: Weertman linear viscous; other powers available for Higher-order |
HYDROLOGY Surface, internal, basal water treatments |
No sliding when base below melt point | Vertical penetration of surface meltwater to the bed, acceleration of basal sliding (optional) | No sliding when base below melting point, does not do any accounting of basal water | Through parameterizations/budgeting |
SURFACE MASS BALANCE Positive degree day; Surface energy balance; empirical method; other |
Positive degree day | Positive degree day | Positive degree day | PDD |
CALVING Calving "law"; calving mechanics |
ocean sub-ice melt rate prescribed | Several calving laws for marine ice, ice shelves currently under construction. | Several mean-field "calving laws"implemented, heuristic implementation of rift initiation and propagation | Will be added; presently thickness related |
SPIN-UP/INITIALIZATION # glacial cycles; req'd initial fields |
can be run for many glacial cycles | Arbitrary number of glacial cycles (at least one). | Can be run over many glacial cycles, Initial parameters: surface elevation, bedrock elevation, geothermal flux, location/depth of sediment | This depends on the experiment as stated in my earlier email. If thermal profile and melt/freeze boundaries matter to the simulation, 250kyr of thermal spin-up and then one or two glacial cycles; need bed elevation, surface elevation, surface temp (mean annual and summer average), surface accum, geothermal flux, upper mantle viscosity, some sense of distribution of basal friction coeff, sea level fluctuation, and any glacial geologic constraints on reconstructions |
OTHER Explicit mass conservation |
conserves mass | SIA: Diffusion formulation, method 3 (Hindmarsh and Payne, Ann. Glaciol. 23, 1996) | no | diffusion formulation for SIA; advection for higher order |
Grounding line migration | yes | Currently under construction | yes - with concerns about stability | yes |
Publication describing the model (if available) | Pollard, D. and R.M. DeConto. 2009. Modelling West Antarctic ice sheet growth and collapse through the past five million years. Nature, 458, 329-332. | Greve, R., 2007. Ice-sheet model SICOPOLIS. Hokkaido University Collection of Scholarly and Academic Papers (HUSCAP), URL http://hdl.handle.net/2115/34755 [not entirely up-to-date!]. |
Table 1 (Cont 2). Characteristics of Various Whole Ice-Sheet Models
Characteristics | IcIES | Elmer/Ice | GRISLI | AIF |
---|---|---|---|---|
Domain Flowline (1d or 2D); Plan view (2D or 3D) |
3D | 3D | 3D | 3D |
SPACING Average grid spacing; Adaptive grid |
uniform >=5km | adaptive | uniform >=10km | uniform >=5km |
GRID Finite-difference; Finite-element; Eulerian/Lagrangian |
FD | FE, Eulerian | FD, Eulerian | FD |
FLOW APPROXIMATION Shallow ice; Shelfy-Stream; Higher-order; Full Stokes; other |
SIA | Full Stokes | Hybrid model : SIA + Shallow shelf/stream + eventually a mixture of both. | SIA + longitudinal stresses |
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical | Thermomechanical (including ice shelves) | Thermomechanical |
BASAL SLIDING Weertman sliding law; Coulomb plastic sliding law; Budd-type sliding law | Weertman 3rd power | Weertman, optional sub-melt sliding | Flexible , depends on basal water pressure | adjustable Weertman-type, Budd-type sliding law |
HYDROLOGY Surface, internal, basal water treatments |
None | Hydrology diffusion equation (Darcy law) | enhanced basal sliding induced by surface melt water | |
SURFACE MASS BALANCE Positive degree day; Surface energy balance; empirical method; other |
Positive degree-day | Positive degree-day | Positive degree-day | Positive degree-day |
CALVING Calving "law"; calving mechanics |
minimum thickness + semi-lagrangian scheme for the front | under construction | ||
SPIN-UP/INITIALIZATION # glacial cycles; req'd initial fields |
At least one glacial cycle | Relaxation of spinup fields from SICOPOLIS | Can be run over many glacial cycles | Can be run over many glacial cycles. For SeaRISE experiments, forcing the model to match the currently observed fields is used for the model initialization. |
OTHER Explicit mass conservation |
Yes | Yes, solves the transport equation | Yes | |
Grounding line migration | No | Yes | Yes | |
Publication describing the model (if available) | Saito and Abe-Ouchi (2005,2010),etc | Seddik et al. 2012 | Ritz et al, JGR. 2001 (many improvements since that time) |
Table 1. (Cont.3) Characteristics of Various Whole Ice-Sheet Models
Characteristics | PISM-PIK | ISSM link | ........ | ........ | ........ |
---|---|---|---|---|---|
Domain Flowline (1d or 2D); Plan view (2D or 3D) |
3D (see PISM) | 3D | |||
SPACING Average grid spacing; Adaptive grid |
adjustable; non-adaptive grid (see PISM) | Adaptive grid spacing (between 1km on the coast and 25 km inside the continent) | |||
GRID Finite-difference; Finite-element; Eulerian/Lagrangian |
Eulerian; finite-difference (see PISM) | Finite elements; ALE (Arbitrary Lagrangian-Eulerian) | |||
FLOW APPROXIMATION Shallow ice; Shelfy-Stream; Higher-order; Full Stokes; other |
Hybrid model: Shallow ice (SIA) + Shelfy-Stream (Schoof) (see PISM) | Shallow ice, Shelfy-Stream Higher-order or Full-Stokes | |||
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical | |||
BASAL SLIDING Weertman sliding law; Coulomb plastic sliding law; Budd-type sliding law |
Coulomb plastic or Weertman (see PISM) | Coulomb sliding law | |||
HYDROLOGY Surface, internal, basal water treatments |
basal meltwater model | None | |||
SURFACE MASS BALANCE Positive degree day; Surface energy balance; empirical method; other |
fixed surface mass balance field | Imposed surface mass balance | |||
CALVING Calving "law"; calving mechanics |
Dynamic Calving Law | Fixed-front | |||
SPIN-UP/INITIALIZATION # glacial cycles; req'd initial fields |
~300 kyrs spinup to equilibrium | data assimilation to match present-day velocities and thermomechanical steady state (consistent velocities and temperature) | |||
OTHER Explicit mass conservation |
yes, adaptive time-step (see PISM) | yes | |||
Grounding line migration | yes (see PISM) | yes | |||
Publication describing the model (if available) | The Potsdam Parallel Ice Sheet Model (PISM-PIK) (Parts 1 and 2), TCD, 4, 2010:
Winkelmann et al: Model description. Martin et al: Dynamic equilibrium simulation of the Antarctic ice sheet. |
See ISSM publications |