Participating Models

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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