ismip7_run

The landice/ismip7_run test group sets up one or more experiments from the ISMIP7 protocol for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GrIS).

This functionality assumes the forcing files have already been generated using the ismip7_forcing test group and organized into the expected directory layout. It creates a consistent set of run directories for the requested experiments. Each experiment directory is self-contained with namelists, streams, forcing symlinks, and a job script ready for submission.

The test group includes two test cases:

  • ismip7_ais — Antarctic Ice Sheet experiments

  • ismip7_gris — Greenland Ice Sheet experiments

Note

This test group is not meant for automated running of experiments. Expert knowledge is recommended for conducting the actual simulations. Each experiment (step) should be submitted manually via its job script.

Experiment Matrix

The ISMIP7 core protocol defines 11 experiments per ice sheet:

Experiment

Scenario

Start

End

ESM

historical_CESM2-WACCM

Historical

≥1850

2014

CESM2-WACCM

historical_MRI-ESM2-0

Historical

≥1850

2014

MRI-ESM2-0

ssp370_CESM2-WACCM

SSP370

2015

2100

CESM2-WACCM

ssp370_MRI-ESM2-0

SSP370

2015

2100

MRI-ESM2-0

ssp126_CESM2-WACCM

SSP126

2015

2300

CESM2-WACCM

ssp126_MRI-ESM2-0

SSP126

2015

2300

MRI-ESM2-0

ssp585_CESM2-WACCM

SSP585

2015

2300

CESM2-WACCM

ssp585_MRI-ESM2-0

SSP585

2015

2300

MRI-ESM2-0

ctrl_CESM2-WACCM

CTRL2015

2015

2300

CESM2-WACCM

ctrl_MRI-ESM2-0

CTRL2015

2015

2300

MRI-ESM2-0

ocx

OCX

1990

2025

(reanalysis)

Unlike ISMIP6, ISMIP7 requires a separate historical simulation per ESM. Projection experiments automatically symlink their restart file from the corresponding ESM’s historical run (e.g., ssp585_CESM2-WACCM → ../historical_CESM2-WACCM/rst.2015-01-01.nc).

Usage

  1. Process forcing data using ismip7_forcing.

  2. Organize output into the expected directory layout:

    {forcing_basepath}/
├── CESM2-WACCM_historical/
│   ├── atmosphere/
│   │   └── {mesh}_SMB_CESM2-WACCM_historical_*.nc
│   ├── ocean_thermal_forcing/
│   │   └── {mesh}_2dThermalForcing_*.nc  (GrIS)
│   │   └── {mesh}_3dThermalForcing_*.nc  (AIS; optional for GrIS)
│   └── shelf_collapse/
│       └── {mesh}_ice_shelf_collapse_mask_*.nc
├── CESM2-WACCM_ssp585/
│   ├── atmosphere/
│   ├── ocean_thermal_forcing/
│   └── shelf_collapse/
└── ...

    The shelf_collapse subdirectory (ISMIP7 Path C ice shelf collapse mask, produced by fracture) is required for ssp* experiments unless use_hydrofracture_forcing is set to false; see Mask Calving (Path C) below.

  3. Create a user config file overriding the NotAvailable paths.

  4. Set up and run:

    compass setup landice/ismip7_run/ismip7_ais -f my_ismip7_ais.cfg
# Then submit job scripts from individual experiment directories

    If gia_model is set to 1dSLM or FastIsostasy, compass setup also adds a mapping_files or fastiso_mapping_files subdirectory (respectively). These must be run (via their job script, or compass run from within that subdirectory) before submitting any individual experiment, since the experiments’ job scripts assume the mapping files already exist.

config options

All config options should be reviewed and altered as needed.

AIS config ([ismip7_run_ais]):

[ismip7_run_ais]

# Experiment list: "all", "historical", "projections", "ctrl",
# or comma-delimited experiment names
exp_list = all

# Number of MPI tasks
ntasks = 128
pio_stride = 128

# Base path to pre-processed forcing
forcing_basepath = NotAvailable

 # Initial condition and parameter files
 init_cond_path = NotAvailable
 melt_params_path = NotAvailable
 reference_surface_path = NotAvailable
 region_mask_path = NotAvailable

# Climatology files for CTRL2015 experiments
ctrl_tf_climatology_path = NotAvailable
ctrl_atm_climatology_path = NotAvailable

# OCX forcing path
ocx_forcing_path = NotAvailable

# Calving: restore or von_mises
calving_method = restore
von_mises_parameter_path = NotAvailable

# Whether to apply the ISMIP7 Path C ice shelf collapse mask as
# hydrofracture-gated mask calving (not used for historical, ctrl, or
# ocx experiments). If true, setup fails when the mask file is missing
# for an experiment that should have one.
use_hydrofracture_forcing = true

# Ice fracture toughness (Pa m^0.5) for the hydrofracture vulnerability
# criterion gating mask calving, used only when use_hydrofracture_forcing
# is true.
calving_fracture_toughness = 2.0e5

# Face melting
use_face_melting = false

# Glacial isostatic adjustment (GIA) coupling: none, 1dSLM, or FastIsostasy
gia_model = none

# Sea-level model coupling (used if gia_model = 1dSLM)
slm_input_ice = NotAvailable
slm_input_earth = NotAvailable
slm_earth_structure = prem_512.l60K2C.sum18p6.dum19p2.tz19p4.lm22
slm_input_others = NotAvailable
nglv = 2048

# FastIsostasy (regional bedrock/GIA) coupling (used if
# gia_model = FastIsostasy)
fastiso_path = NotAvailable
fastiso_earth_structure_filename = weak-earth.nc
fastiso_mask_filename = None
fastiso_res_km = 8

Note

fastiso_res_km sets the resolution (in km) of the regular grid FastIsostasy runs on, which should match one of the standard ISMIP7 grid resolutions (2, 4, 8, or 16 km for AIS). As of this writing, resolutions finer than 8 km have been found to yield numerically unstable results.

Note

fastiso_path is a directory holding both the Earth-structure (rheology) file named by fastiso_earth_structure_filename and, optionally, an interactive-sea-level activation mask file named by fastiso_mask_filename. Leaving fastiso_mask_filename = None uses FastIsostasy’s built-in fallback, which activates interactive sea level only over the un-padded ice domain – a hard cutoff at the domain/padding boundary that can show up as a ring-shaped artifact in bed-topography change near the edge of the ice sheet. Supplying a mask file (NetCDF with dims x/y, 1-D coordinate variables x/y in meters, and a 2-D variable M) lets you activate it over a wider region, e.g. the full padded domain, instead.

GrIS config ([ismip7_run_gris]) is similar (including reference_surface_path) but without sea-level model or FastIsostasy coupling options, and adds use_3d_thermal_forcing (default false):

# Whether to additionally force with 3D ocean thermal forcing (built by
# the build_3d_thermal_forcing step of landice/ismip7_forcing/ocean_thermal)
# alongside the 2D forcing. Requires melt_params_path.
use_3d_thermal_forcing = false

GrIS always reads ismip6_2dThermalForcing (the authoritative ISMIP7 2D ocean forcing) from *2dThermalForcing_*.nc at monthly intervals. When use_3d_thermal_forcing is true, it additionally reads ismip6shelfMelt_3dThermalForcing and ismip6shelfMelt_zOcean from *3dThermalForcing_*.nc at monthly intervals (the 3D forcing is split across multiple year-block files addressed via a $Y template), plus ismip6shelfMelt_deltaT, ismip6shelfMelt_basin, and ismip6shelfMelt_gamma0 from the file at melt_params_path (which must be supplied in that case).

Forcing Streams

ISMIP7 uses more forcing fields than ISMIP6, at mixed temporal resolutions:

Monthly forcing (input_interval = 0000-01-00_00:00:00):

  • sfcMassBal — surface mass balance

  • surfaceAirTemperature — surface air temperature

  • ismip6Runoff — ice sheet runoff

  • ismip6_2dThermalForcing (GrIS, always) — 2D ocean thermal forcing

  • ismip6shelfMelt_3dThermalForcing (GrIS when use_3d_thermal_forcing = true) — 3D ocean thermal forcing

Annual forcing (input_interval = 0001-00-00_00:00:00):

  • sfcMassBalLapseRate — SMB elevation lapse rate

  • surfaceAirTemperatureLapseRate — temperature lapse rate

  • ismip6shelfMelt_3dThermalForcing (AIS, always) — 3D ocean thermal forcing

Static (input_interval = initial_only):

  • ismip6shelfMelt_zOcean — ocean depth coordinates (AIS; GrIS when use_3d_thermal_forcing = true)

  • ismip6shelfMelt_deltaT, ismip6shelfMelt_basin, ismip6shelfMelt_gamma0 — melt parameterization coefficients

For CTRL2015 experiments, all forcing intervals are set to initial_only (constant climate).

Mask Calving (Path C)

ismip7_ais can optionally apply the ISMIP7 Path C ice shelf collapse mask produced by fracture. The mask is looked up under the same forcing_basepath used for the atmosphere/ocean forcing, at {forcing_basepath}/{model}_{scenario}/shelf_collapse/*ice_shelf_collapse_mask_*.nc. historical, ctrl, and ocx experiments never use this pathway, regardless of use_hydrofracture_forcing.

When use_hydrofracture_forcing is true (the default) for any other experiment (e.g. ssp126, ssp370, ssp585), a matching mask file is required: if it is missing, compass setup fails with an error rather than silently skipping mask calving. When found, the mask is symlinked into the run directory and used to force calving:

  • config_apply_calving_mask is set to .true.

  • config_restore_calving_front is set to .false.

  • config_require_extensional_stresses_for_mask_calving is set to .true., so the mask only removes floating ice that is also vulnerable to hydrofracture per the fracture-toughness criterion of Lai et al. (2020) / Reynolds and Nowicki (2026). The threshold depends on config_calving_fracture_toughness.

Set use_hydrofracture_forcing = false to disable mask calving and the hydrofracture gating entirely; experiments then use their normal calving_method configuration instead.

ismip7_ais

landice/ismip7_run/ismip7_ais sets up AIS experiments with 3D ocean thermal forcing (30 vertical layers) and optional sea-level model and/or FastIsostasy coupling.

ismip7_gris

landice/ismip7_run/ismip7_gris sets up GrIS experiments with 2D (depth-averaged) ocean thermal forcing (always), plus optional 3D forcing (matching the AIS convention) when use_3d_thermal_forcing = true and the GrIS build_3d_thermal_forcing step (see ocean_thermal) has been run. Both the 2D and 3D forcings are delivered to MALI simultaneously when 3D is enabled. Sea-level model coupling is not currently supported for GrIS. Crevasse-depth calving is the default.