Participating Models
From Interactive System for Ice sheet Simulation
Since posting Table 1, additional whole ice sheet models interested in SeaRISE participation are:
- ELMER (Hakime Seddik)
- Texas (Ren Diadong)
- Goddard (Weili Wang)
- GRISLI (Catherine Ritz)
- PISM-PIK (Maria Martin)
Table 1. Characteristics of Various Whole Ice-Sheet Models
Characteristics | Glimmer | CISM est. Q2 2009 | PISM | 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 | adjustable; non-adaptive 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: Shallow ice (SIA) + Shelfy-Stream (Schoof) | shallow ice | 1st – order SIA (e.g. Pattyn/Blatter models) |
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical + Polythermal of Greve | Thermomechanical + Polythermal (Enthalpy Formulation) | 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 | 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 | 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) |
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 | Greenland, Antarctica or northern/southern hemisphere from tropics to the Pole 3D | flowline and plan view mode | flowline, 2-d |
SPACING Average grid spacing; Adaptive grid |
40 km, or nested 10 km to 5 km | 10 km for Greenland; 20 km for Antarctica | 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 | Finite difference; stereographic projection or lat/log grid | 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 | Shallow ice | Other | SIA ready to go, Higher-order ready in isothermal mode |
THERMODYNAMICS Thermomechanical; Polythermal |
Thermomechanical | Thermomechanical; can be ran as polythermal (but I did not run it myself as polythermal) | Thermomechanical | SIA: thermomechanical; Higher-order: presently isothermal |
BASAL SLIDING Weertman sliding law; Coulomb plastic sliding law; Budd-type sliding law | Weertman sliding law | Weertman sliding law | 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 | 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, but Miren Vizcaino ran it also with a of surface energy balance | Positive degree day | PDD |
CALVING Calving "law"; calving mechanics |
ocean sub-ice melt rate prescribed | No explicit calving (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 | glacial cycles or topography + T(z) | 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 | no | no | diffusion formulation for SIA; advection for higher order |
Grounding line migration | yes | no (under construction) | yes - with concerns about stability | yes |