ismip7_forcing

The landice/ismip7_forcing test group processes (i.e., remaps and renames) the atmospheric and ocean thermal forcing data of the Ice Sheet Model Intercomparison for CMIP7 (ISMIP7) protocol. The processed data is used to force MALI in its simulations under the ISMIP7 experimental protocol. The test group supports both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GrIS), controlled by a single ice_sheet config option.

The test group includes two test cases: atmosphere and ocean_thermal.

  • The atmosphere test case has five steps: process_smb, process_temperature, process_smb_gradient, process_temperature_gradient, and process_runoff.

  • The ocean_thermal test case has one step: process_thermal_forcing. For AIS this produces 3D thermal forcing (with 30 ocean depth layers); for GrIS it produces 2D (depth-averaged) thermal forcing.

(For more details on the steps of each test case, see atmosphere and ocean_thermal.)

Usage

To use this test group, users need to:

  1. Provide a MALI mesh file onto which the source data will be remapped.

  2. Set the ice_sheet config option to either ais or gis.

  3. Provide the path to the ISMIP7 forcing data (base_path_ismip7).

  4. Run the atmosphere test case for each model and scenario combination.

  5. Run the ocean_thermal test case for each model and scenario combination.

Input Data

ISMIP7 forcing data is organized by variable and version. The expected directory structure under base_path_ismip7 is:

For AIS atmosphere (2km, polar stereographic EPSG:3031):

acabf/v2/acabf_AIS_{model}_{scenario}_SDBN1-2000m_v2_{year_range}.nc
ts/v2/ts_AIS_{model}_{scenario}_SDBN1-2000m_v2_{year_range}.nc
dacabfdz/v2/dacabfdz_AIS_{model}_{scenario}_SDBN1-2000m_v2_{year_range}.nc
dtsdz/v2/dtsdz_AIS_{model}_{scenario}_SDBN1-2000m_v2_{year_range}.nc
mrro/v2/mrro_AIS_{model}_{scenario}_SDBN1-2000m_v2_{year_range}.nc

For AIS ocean thermal (8km, 30 depth levels, decade files):

ocean/tf/v3/tf_AIS_{model}_{scenario}_ocean_v3_{start_year}-{end_year}.nc

For GrIS atmosphere (1km, polar stereographic EPSG:3413):

acabf/v2/acabf_GrIS_{model}_{scenario}_SDBN1-1000m_v2_{year}.nc
ts/v2/ts_GrIS_{model}_{scenario}_SDBN1-1000m_v2_{year}.nc
dacabfdz/v2/dacabfdz_GrIS_{model}_{scenario}_SDBN1-1000m_v2_{year}.nc
dtsdz/v2/dtsdz_GrIS_{model}_{scenario}_SDBN1-1000m_v2_{year}.nc
mrro/v2/mrro_GrIS_{model}_{scenario}_SDBN1-1000m_v2_{year}.nc

For GrIS ocean thermal (same 1km grid, 2D, yearly files):

ocean/tf/v2/tf_GrIS_{model}_{scenario}_ocean_v2_{year}.nc

config options

The ismip7_forcing test group uses three config sections. The default values are:

# config options for ismip7 forcing data
[ismip7]

# Ice sheet: ais (Antarctic) or gis (Greenland)
ice_sheet = NotAvailable

# Base path to the input ISMIP7 forcing files
base_path_ismip7 = NotAvailable

# Base path to the MALI mesh
base_path_mali = NotAvailable

# Base path to which output forcing files are saved
output_base_path = NotAvailable

# Name of climate model (e.g., CESM2-WACCM, MRI-ESM2-0)
model = NotAvailable

# Scenario (e.g., historical, ssp126, ssp370, ssp585)
scenario = NotAvailable

# Name of the MALI mesh (used in output file naming)
mali_mesh_name = NotAvailable

# MALI mesh file name
mali_mesh_file = NotAvailable

# Number of MPI tasks for ESMF_RegridWeightGen
esmf_ntasks = 128

# config options for ismip7 atmosphere forcing
[ismip7_atmosphere]

# Remapping method: bilinear, neareststod, conserve
method_remap = conserve

# Start year for processing
start_year = 1850

# End year for processing
end_year = 2014

# config options for ismip7 ocean thermal forcing
[ismip7_ocean_thermal]

# Remapping method: bilinear, neareststod, conserve
method_remap = bilinear

# Start year for processing
start_year = 1850

# End year for processing
end_year = 2014

All NotAvailable options must be overridden in a user config file passed at setup time (e.g., compass setup ... -f my_ismip7.cfg).

atmosphere

The landice/ismip7_forcing/atmosphere test case processes the ISMIP7 atmosphere forcing fields and remaps them from the native polar stereographic grid to the MALI unstructured mesh.

Steps:

  • process_smb: Remaps the surface mass balance (acabf) field. The output variable is sfcMassBal.

  • process_temperature: Remaps the surface temperature (ts) field, clipped to a maximum of 273.15 K. The output variable is surfaceAirTemperature.

  • process_smb_gradient: Remaps the SMB lapse rate (dacabfdz) field. The output variable is sfcMassBalLapseRate.

  • process_temperature_gradient: Remaps the temperature lapse rate (dtsdz) field. The output variable is surfaceAirTemperatureLapseRate.

  • process_runoff: Remaps the ice sheet runoff (mrro) field. The output variable is ismip6Runoff.

ocean_thermal

The landice/ismip7_forcing/ocean_thermal test case processes the ISMIP7 ocean thermal forcing (tf) and remaps it from the native polar stereographic grid to the MALI unstructured mesh.

For AIS, thermal forcing is 3D with 30 vertical ocean layers. The input files span decades (e.g., 1850-1859). The output variable is ismip6shelfMelt_3dThermalForcing with dimension nISMIP6OceanLayers. Associated depth coordinate variables ismip6shelfMelt_zOcean and ismip6shelfMelt_zBndsOcean are also produced.

For GrIS, thermal forcing is 2D (depth-averaged), with monthly temporal resolution and yearly input files. The output variable is ismip6_2dThermalForcing.