With four parameters I can fit an elephant, and with five I can make him wiggle his trunk.
John von Neumann
| Flag name | Default value | Description |
| bmr_enhance_basal_water_pressure | "no" | if 'yes' then add basal melt rate enhancement to determination of basal water pressure, which normally only depends on effective thickness of basal water (=bwat) |
| calving_front_stress_boundary_condition | "no" | Apply CFBC condition as in [Albrechtetal2011, Winkelmannetal2010TCD]. May only apply to some stress balances; e.g. SSAFD as of May 2011. If not set then a strength-extension is used, as in [BBssasliding]. |
| compute_grain_size_using_age | "no" | Use age of the ice to compute grain size to use with the Goldsby-Kohlstedt [GoldsbyKohlstedt] flow law |
| compute_surf_grad_inward_ssa | "no" | [missing] |
| correct_cell_areas | "yes" | Compute corrected cell areas using WGS84 datum (for ice area and volume computations). |
| count_time_steps | "no" | If yes, IceModel::run() will count the number of time steps it took. Sometimes useful for performance evaluation. Counts all steps, regardless of whether processes (mass continuity, energy, velocity, ...) occurred within the step. |
| dirichlet_bc | "no" | apply Dirichlet boundary condition |
| do_age | "no" | Solve age equation (advection equation for ice age). |
| do_cold_ice_methods | "no" | Use cold ice (i.e. not polythermal) methods. |
| do_eigen_calving | "false" | calculate strain rates and related calving rate |
| do_energy | "yes" | Solve energy conservation equations. |
| do_mass_conserve | "yes" | Solve the mass conservation equation |
| do_pseudo_plastic_till | "no" | Use the pseudo-plastic till model. |
| do_sia | "yes" | Use the SIA stress balance (possibly as a part of a hybrid). |
| do_skip | "no" | Use the temperature, age, and SSA stress balance computation skipping mechanism. |
| do_ssa_enhancement | "no" | Set an enhancement factor for SSA-calculation. |
| do_thickness_calving | "false" | ad hoc calving at certain threshold for terminal ice thickness |
| floating_ice_killed | "false" | If ice is (or becomes) floating then it is set to thickness zero. This is calving at the grounding line. |
| force_full_diagnostics | "no" | Force full diagnostic output (adds 3D velocity fields and velocity components at the surface |
| force_output_times | "yes" | Modify the time-stepping mechanism to hit times requested using -extra_times and -ts_times. |
| include_bmr_in_continuity | "yes" | Include basal melt rate in the continuity equation |
| interpret_precip_as_snow | "no" | Interpret precipitation as snow fall. |
| is_dry_simulation | "no" | Dry (ocean-less) simulation |
| kill_icebergs | "no" | identify and kill detached ice-shelf areas |
| ocean_kill | "false" | If used with input from a NetCDF initialization file which has ice-free ocean mask, will zero out ice thicknesses in areas that were ice-free ocean at time zero. This is calving at the location of the original calving front. |
| part_grid | "no" | apply partially filled grid cell scheme |
| part_redist | "no" | for partially filled grid cell scheme, redistribute residuals Hresidual |
| pdd_limit_timestep | "false" | Limit PDD time-step to 1 year; used by pclimate to make long runs faster. Is not and should not be used elsewhere. |
| thermal_bedrock | "yes" | Use the bedrock thermal model |
| thk_eff_basal_water_pressure | "no" | if 'yes' then modeled basal water pressure experiences decreases at locations where thickness is smaller than thk_eff_H_high (typically near margin; thickness is surrogate for distance to margin) |
| use_constant_nuh_for_ssa | "no" | Compute velocities in ice shelves and streams with a constant value for the product of viscosity  and thickness  , obtained from the shelf extension |
| use_ssa_velocity | "no" | Use the equations of the shallow shelf approximation [MacAyeal, Morland, SchoofStream, WeisGreveHutter] for ice shelves and dragging ice shelves (i.e. ice streams) where so-indicated by the mask |
| use_ssa_when_grounded | "no" | The SSA can be used as a sliding law for grounded ice [BBssasliding], and it is if this is yes. |
| verification_mode | "no" | ; shows whether PISM is running in the verification mode |
| write_ssa_system_to_matlab | "no" | Specifies whether to write the SSA system to a matlab file |
| Parameter name | Default value | Description |
| Glen_exponent | 3 | ; Glen exponent in ice flow law |
| Hooke_A | 4.421650e-09 | s-1 Pa-3; A_Hooke = (1/B_0)^n where n=3 and B_0 = 1.928 a^(1/3) Pa. See [Hooke] |
| Hooke_C | 0.166120 | Kelvin^Hooke_k; See [Hooke] |
| Hooke_Q | 78800 | J / mol; Activation energy, see [Hooke] |
| Hooke_Tr | 273.390000 | Kelvin; See [Hooke] |
| Hooke_k | 1.170000 | ; See [Hooke] |
| Paterson-Budd_A_cold | 3.610000e-13 | Pa^-3 / s; Paterson-Budd A_cold, see [PatersonBudd] |
| Paterson-Budd_A_warm | 1730 | Pa^-3 / s; Paterson-Budd A_warm, see [PatersonBudd] |
| Paterson-Budd_Q_cold | 60000 | J/mol; Paterson-Budd Q_cold, see [PatersonBudd] |
| Paterson-Budd_Q_warm | 139000 | J/mol; Paterson-Budd Q_warm, see [PatersonBudd] |
| Paterson-Budd_critical_temperature | 263.150000 | Kelvin; Paterson-Budd critical temperature, see [PatersonBudd] |
| Schoof_regularizing_length | 1000 | km; Regularizing length (Schoof definition) |
| Schoof_regularizing_velocity | 1 | m/year; Regularizing velocity (Schoof definition) |
| WGS84_semimajor_axis | 6378137 | m; WGS84 reference ellipsoid semi-major axis |
| WGS84_semiminor_axis | 6356752.314245 | m; WGS84 reference ellipsoid semi-minor axis |
| adaptive_timestepping_ratio | 0.120000 | ; Adaptive time stepping ratio for the explicit scheme for the mass balance equation; BBL, inequality (25) |
| air_temp_all_precip_as_rain | 274.150000 | Kelvin; threshold temperature above which all precipitation is rain; must exceed air_temp_all_precip_as_snow to avoid division by zero, because difference is in a denominator |
| air_temp_all_precip_as_snow | 272.150000 | Kelvin; threshold temperature below which all precipitation is snow |
| backup_interval | 1 | hours; wall-clock time between automatic backups |
| bed_def_interval_years | 10 | years; Interval between bed deformation updates |
| bed_smoother_range | 5000 | m; half-width of smoothing domain for PISMBedSmoother, in implementing [Schoofbasaltopg2003] bed roughness parameterization for SIA; set value to zero to turn off mechanism |
| bedrock_thermal_conductivity | 3 | J m-1 K-1 s-1; = W m-1 K-1; for bedrock used in thermal model [RitzEISMINT] |
| bedrock_thermal_density | 3300 | kg m-3; for bedrock used in thermal model |
| bedrock_thermal_specific_heat_capacity | 1000 | J kg-1 K-1; for bedrock used in thermal model [RitzEISMINT] |
| beta_CC | 7.900000e-08 | K Pa-1; Clausius-Clapeyron constant [Luethi2002] |
| beta_ice_free_bedrock | 1.800000e+09 | Pa s m-1; value is for ice stream E from [ ef HulbeMacAyeal]; thus sliding velocity, but we hope it doesn't matter much; at 100 m a-1 the linear sliding law gives 57040 Pa basal shear stress |
| bmr_enhance_scale | 3.168876e-07 | m s-1; = 10.0 m a-1; level at which basal melt rate starts making major difference in water pressure |
| bootstrapping_BCMask_value_no_var | 0 | ; mask for dirichlet boundary condition |
| bootstrapping_BCvel_value_no_var | 100 | ; dirichlet boundary condition |
| bootstrapping_H_value_no_var | 0 | m; thickness value to use if thk (land_ice_thickness) variable is absent in bootstrapping file |
| bootstrapping_Hmelt_value_no_var | 0 | m; basal melt water effective thickness value to use if variable Hmelt is absent in bootstrapping file |
| bootstrapping_bed_value_no_var | 1 | m; bed elevation value to use if topg (bedrock_altitude) variable is absent in bootstrapping file |
| bootstrapping_bmelt_value_no_var | 0 | m s-1; basal melt rate value to use if variable bmelt is absent in bootstrapping file |
| bootstrapping_geothermal_flux_value_no_var | 0.042000 | W m-2; geothermal flux value to use if bheatflx variable is absent in bootstrapping file |
| bootstrapping_tillphi_value_no_var | 15 | degrees; till friction angle value to use if variable tillphi is absent in bootstrapping file; tends not to slip |
| bootstrapping_uplift_value_no_var | 0 | m s-1; uplift value to use if dbdt variable is absent in bootstrapping file |
| calving_at_thickness | 50 | When terminal ice thickness of floating ice shelf is less than this threshold, it will be calved off. |
| climate_forcing_buffer_size | 60 | ; number of 2D climate forcing records to keep in memory; = 5 years of monthly records |
| cold_mode_is_temperate_ice_tolerance | 0.001000 | Kelvin; Tolerance within which ice is treated as temperate (cold-ice mode only). |
| constant_grain_size | 1 | mm; Default constant grains size to use with the Goldsby-Kohlstedt [GoldsbyKohlstedt] flow law |
| constant_nu_strength_extension_ssa | 9.486807e+14 | Pa s; The SSA is made elliptic by use of a constant value for the product of viscosity (nu) and thickness (H). This value for nu comes from hardness (bar B)=1.9e8 Pa s^(1/3) [MacAyealetal] and a typical strain rate of 0.001 a-1: nu = (bar B) / (2 * 0.001^(2/3)). Compare the value of 9.45e14 Pa s = 30 MPa yr in [Ritzetal2001]. |
| default_tauc | 200000 | Pa; fill value for yield stress for basal till (plastic or pseudo-plastic model); note 2 x 10^5 Pa = 2.0 bar is quite strong and little sliding should occur without an explicit tauc choice altering this default |
| default_till_phi | 30 | degrees; fill value for till friction angle |
| drainage_max_rate | 1.584438e-09 | s-1; = 0.05 a-1; maximum rate at which liquid water fraction in temperate ice could possibly drain; see [AschwandenBuelerKhroulevBlatter] |
| drainage_target_water_frac | 0.010000 | ; liquid water fraction (omega) above which drainage occurs, but below which there is no drainage; see [AschwandenBuelerKhroulevBlatter] |
| eigen_calving | 0 | Set proportionality constant to determine calving rate from strain rates |
| enhancement_factor | 1 | ; Flow enhancement factor for SIA |
| enthalpy_cold_bulge_max | 60270 | J kg-1; = (2009 J kg-1 K-1) * (30 K); maximum amount by which advection can reduce the enthalpy of a column of ice below its surface enthalpy value |
| enthalpy_converter_reference_temperature | 223.150000 | K; = T_0 in enthalpy formulas in [AschwandenBuelerKhroulevBlatter] |
| enthalpy_temperate_conductivity_ratio | 0.100000 | pure number; K in cold ice is multiplied by this fraction to give K0 in [AschwandenBuelerKhroulevBlatter] |
| epsilon_ssafd | 1.000000e+15 | initial amount of (denominator) regularization in computation of effective viscosity, in SSAFD object |
| force_to_thickness_alpha | 6.337753e-11 | s-1; = 0.002 a-1; exponential coefficient in force-to-thickness mechanism |
| fresh_water_density | 1000 | kg m-3; |
| global_min_allowed_temp | 200 | Kelvin; Minimum allowed ice temperature |
| gpbld_water_frac_coeff | 181.250000 | ; coefficient in Glen-Paterson-Budd flow law for extra dependence of softness on liquid water fraction (omega) [GreveBlatter2009, LliboutryDuval1985] |
| gpbld_water_frac_observed_limit | 0.010000 | ; maximum value of liquid water fraction omega for which softness values are parameterized by [LliboutryDuval1985]; used in Glen-Paterson-Budd-Lliboutry-Duval flow law; compare [AschwandenBuelerKhroulevBlatter] |
| grid_Lbz | 0 | meters; Thickness of the thermal bedrock layer. |
| grid_Lx | 1500000 | m; Default computational box is 3000 km x 3000 km (= 2 Lx x 2 Ly) in horizontal. |
| grid_Ly | 1500000 | m; Default computational box is 3000 km x 3000 km (= 2 Lx x 2 Ly) in horizontal. |
| grid_Lz | 4000 | meters; Height of the computational domain. |
| grid_Mbz | 1 | ; Number of thermal bedrock layers; 1 level corresponds to no bedrock. |
| grid_Mx | 61 | ; Number of grid points in the x direction. |
| grid_My | 61 | ; Number of grid points in the y direction. |
| grid_Mz | 31 | ; Number of vertical grid levels in the ice. |
| grid_lambda | 4 | ; Vertical grid spacing parameter. Roughly equal to the factor by which the grid is coarser at an end away from the ice-bedrock interface. |
| hmelt_decay_rate | 3.168876e-11 | m s-1; = 1 m per 1000 years; rate at which bwat is reduced to zero, in absence of other effects like basal melt rate |
| hmelt_max | 2 | meters; maximum thickness of the basal melt water layer |
| ice_density | 910 | kg m-3; = rho_i; density of ice in ice sheet |
| ice_softness | 4.000000e-25 | Pa-3 s-1; ice softness used by CustomGlenIce |
| ice_specific_heat_capacity | 2009 | J kg-1 K-1; at melting point T_0 |
| ice_thermal_conductivity | 2.100000 | J m-1 K-1 s-1; = W m-1 K-1 |
| ideal_gas_constant | 8.314410 | J mol-1 K-1; ideal gas constant |
| initial_age_of_ice_years | 0 | years; Initial age of ice |
| lithosphere_density | 3300 | kg m-3; lithosphere density used by the bed deformation model. See [LingleClark, BLKfastearth] |
| lithosphere_flexural_rigidity | 5.000000e+24 | N m; lithosphere flexural rigidity used by the bed deformation model. See [LingleClark, BLKfastearth] |
| mantle_viscosity | 1.000000e+21 | Pa s; half-space (mantle) viscosity used by the bed deformation model. See [LingleClark, BLKfastearth] |
| max_iterations_ssafd | 300 | Maximum number of iterations for the ice viscosity computation, in the SSAFD object |
| max_low_temp_count | 10 | Maximum number of grid points with ice temperature below global_min_allowed_temp. |
| maximum_time_step_years | 60 | years; Maximum allowed time step length |
| min_thickness_strength_extension_ssa | 50 | m; The SSA is made elliptic by use of a constant value for the product of viscosity (nu) and thickness (H). At ice thicknesses below this value the product nu*H switches from the normal vertical integral to a constant value. The geometry itself is not affected by this value. |
| minimum_temperature_for_sliding | 273 | K; This is less than water_melting_point_temperature. If ice base is above this value then decide to do SIA sliding, if that mechanism is active at all. |
| mu_sliding | 0 | The sliding law parameter in SIA sliding paradigm. This kind of sliding is not recommended, which is why it is turned off by default. See Appendix B of BBssasliding for the dangers in this mechanism. |
| ocean_sub_shelf_heat_flux_into_ice | 0.500000 | W m-2; = J m-2 s-1; naively chosen default value for heat from ocean; see comments in src/coupler/PISMOcean.cc |
| pdd_factor_ice | 0.008000 | m K-1 day-1; EISMINT-Greenland value [RitzEISMINT] ; = (8 mm ice-equivalent) / (pos degree day) |
| pdd_factor_snow | 0.003000 | m K-1 day-1; EISMINT-Greenland value [RitzEISMINT] ; = (3 mm ice-equivalent) / (pos degree day) |
| pdd_fausto_T_c | 272.150000 | Kelvin; = -1 + 273.15; for formula (6) in [Faustoetal2009] |
| pdd_fausto_T_w | 283.150000 | Kelvin; = 10 + 273.15; for formula (6) in [Faustoetal2009] |
| pdd_fausto_beta_ice_c | 0.015000 | m day-1 K-1; water-equivalent thickness; for formula (6) in [Faustoetal2009] |
| pdd_fausto_beta_ice_w | 0.007000 | m day-1 K-1; water-equivalent thickness; for formula (6) in [Faustoetal2009] |
| pdd_fausto_beta_snow_c | 0.003000 | m day-1 K-1; water-equivalent thickness; for formula (6) in [Faustoetal2009] |
| pdd_fausto_beta_snow_w | 0.003000 | m day-1 K-1; water-equivalent thickness; for formula (6) in [Faustoetal2009] |
| pdd_fausto_latitude_beta_w | 72 | degrees N; latitude below which to use warm case, in formula (6) in [Faustoetal2009] |
| pdd_max_temperature_evals_per_year | 53 | integer; maximum number of times the PDD scheme will ask for temperatures to build location-dependent time series for computing (expected) number of positive degree days; the default means the PDD uses weekly samples of the annual cycle; see also pdd_std_dev |
| pdd_positive_threshold_temp | 273.150000 | K; temperature used to determine meaning of 'positive' degree day |
| pdd_refreeze | 0.600000 | pure fraction; EISMINT-Greenland value [RitzEISMINT] |
| pdd_std_dev | 2.530000 | K; std dev of daily temp variation; value from [Faustoetal2009]; compare EISMINT-Greenland value of 5.0 [RitzEISMINT] |
| pdd_std_dev_lapse_lat_base | 72 | degrees_north; std_dev is a function of latitude, with value pdd_std_dev at this latitude; this value only active if pdd_std_dev_lapse_lat_rate is nonzero |
| pdd_std_dev_lapse_lat_rate | 0 | K degrees_north-1; std_dev is a function of latitude, with rate of change with respect to latitude given by this constant |
| plastic_regularization | 0.010000 | Set the value of  regularization of plastic till; this is the second in formula (4.1) in [SchoofStream] |
| precip_exponential_factor_for_temperature | 0.070417 | Kelvin-1; = 0.169/2.4; in SeaRISE-Greenland formula for paleo-precipitation from present; a 7.3% change of precipitation rate for every one degC of temperature change [Huybrechts02] |
| pseudo_plastic_q | 0.250000 | ; The exponent of the pseudo-plastic basal resistance model |
| pseudo_plastic_uthreshold | 100 | m a-1; |
| run_length_years | 1000 | years; Default run length |
| sea_water_density | 1028 | kg m-3; |
| seconds_per_year | 3.155693e+07 | ; should match the one used by UDUNITS (see src/udunits/pismudunits.dat). |
| skip_max | 10 | Number of mass-balance steps, including SIA diffusivity updates, to perform before a the temperature, age, and SSA stress balance computations are done |
| slice_level | 0 | meters; level (in meters above the base of ice) used in slice viewers |
| sliding_scale_factor_reduces_tauc | -1 | ; divides pseudo-plastic tauc (yield stress) by given factor; this would increase sliding by given factor in absence of membrane stresses; not used if negative or zero; not used by default |
| snow_temp_fausto_c_ma | -0.718900 | Kelvin (degN)-1; latitude-dependence coefficient for formula (1) in [Faustoetal2009] |
| snow_temp_fausto_c_mj | -0.158500 | Kelvin (degN)-1; latitude-dependence coefficient for formula (2) in [Faustoetal2009] |
| snow_temp_fausto_d_ma | 314.980000 | K; = 41.83+273.15; base temperature for formula (1) in [Faustoetal2009] |
| snow_temp_fausto_d_mj | 287.850000 | Kelvin; = 14.70+273.15; base temperature for formula (2) in [Faustoetal2009] |
| snow_temp_fausto_gamma_ma | -0.006309 | Kelvin m-1; = -6.309 / 1km; mean slope lapse rate for formula (1) in [Faustoetal2009] |
| snow_temp_fausto_gamma_mj | -0.005426 | Kelvin m-1; = -5.426 / 1km; mean slope lapse rate for formula (2) in [Faustoetal2009] |
| snow_temp_fausto_kappa_ma | 0.067200 | Kelvin (degW)-1; longitude-dependence coefficient for formula (1) in [Faustoetal2009] |
| snow_temp_fausto_kappa_mj | 0.051800 | Kelvin (degW)-1; longitude-dependence coefficient for formula (2) in [Faustoetal2009] |
| snow_temp_july_day | 196 | day; = day of year for July 15; used in corrected formula (4) in [Faustoetal2009] |
| ssa_enhancement_factor | 1 | ; Flow enhancement factor for SSA |
| ssafd_relative_convergence | 0.000100 | Relative change tolerance for the effective viscosity in the SSAFD object |
| standard_gravity | 9.810000 | m s-2; acceleration due to gravity on Earth geoid |
| start_year | 0 | years; Start year. |
| summary_volarea_scale_factor_log10 | 6 | ; an integer; log base 10 of scale factor to use for volume and area in summary line to stdout |
| surface_pressure | 0 | Pa; atmospheric pressure; = pressure at ice surface |
| thk_eff_H_high | 2000 | m; maximum thickness at which thickness effect on basal water pressure is applied |
| thk_eff_H_low | 1000 | m; thickness at which thickness effect on basal water pressure is full strength |
| thk_eff_reduced | 0.970000 | ; factor by which basal water pressure is reduced by thickness effect |
| till_c_0 | 0 | kPa; cohesion of till; note Schoof uses zero but Paterson pp 168--169 gives range 0--40 kPa; but Paterson notes that '... all the pairs c_0 and phi in the table would give a yield stress for Ice Stream B that exceeds the basal shear stress there...' |
| till_pw_fraction | 0.950000 | pure number; pore water pressure is this fraction of overburden |
| viewer_size | 320 | ; default diagnostic viewer size |
| water_latent_heat_fusion | 334000 | J kg-1; latent heat of fusion for water [AschwandenBlatter] |
| water_melting_point_temperature | 273.150000 | K; melting point of pure water |
| water_specific_heat_capacity | 4170 | J kg-1 Kelvin-1; at melting point T_0 [AschwandenBlatter] |
1.7.3