This file contains information about the data archived for the experiments and figures presented in Lipscomb et al. (2021).  For any questions about this archive, please contact Gunter Leguy at gunterl@ucar.edu.

The experiments use the open-source Community Ice Sheet Model (CISM) (https://github.com/ESCOMP/CISM), and in particular the release called “release-cism2.1.1” (https://doi.org/10.5281/zenodo.4474363).  This release is an update of CISM v2.1, as described by Lipscomb et al. (2019).  The updated version includes new physics options and parameterizations to support the ISMIP6 standalone ice sheet experiments (Nowicki et al., 2020).

Most of the files in this archive have been lossless compressed.

References:

Lipscomb, W. H., Price, S. F., Hoffman, M. J., Leguy, G. R., Bennett, A. R., Bradley, S. L., Evans, K. J., Fyke, J. G., Kennedy, J. H., Perego, M., Ranken, D. M., Sacks, W. J., Salinger, A. G., Vargo, L. J., and Worley, P. H.: Description and evaluation of the Community Ice Sheet Model (CISM) v2.1, Geosci. Model Dev., 12, 387–424, https://doi.org/10.5194/gmd-12-387-2019, 2019.

Lipscomb, W. H., Leguy, G. R., Jourdain, N. C., Asay-Davis, X. A., Seroussi, H. and Nowicki, S.: ISMIP6-based projections of ocean-forced Antarctic Ice Sheet evolution using the Community Ice Sheet Model, The Cryosphere, 15, https://doi.org/10.5194/tc-15-1-2021, 2021.
 
Nowicki, S., Goelzer, H., Seroussi, H., Payne, A. J., Lipscomb, W. H., Abe-Ouchi, A., Agosta, C., Alexander, P., Asay-Davis, X. S., Barthel, A., Bracegirdle, T. J., Cullather, R., Felikson, D., Fettweis, X., Gregory, J. M., Hattermann, T., Jourdain, N. C., Kuipers Munneke, P., Larour, E., Little, C. M., Morlighem, M., Nias, I., Shepherd, A., Simon, E., Slater, D., Smith, R. S., Straneo, F., Trusel, L. D., van den Broeke, M. R., and van de Wal, R.: Experimental protocol for sea level projections from ISMIP6 stand-alone ice sheet models, The Cryosphere, 14, 2331–2368,
https://doi.org/10.5194/tc-14-2331-2020, 2020.
 
 
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#  Main folders in the archive  #
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The archive contains three main folders:

Forcing: contains ocean thermal forcing and ice-shelf collapse files for years 1950–2100.

Spinup: contains the input files used to initialize the spins-ups and the last time slice corresponding to the end of the spin-up (which corresponds to the start of the forward experiments).

Forward: contains the configuration files used for each experiment, a history file with output at year 2500, a restart file corresponding to year 2500, and scalar time series spanning 1950–2500. This folder contains subfolders for control experiments (without ocean forcing anomalies) and for experiments that apply ocean thermal forcing anomalies from Earth system models (ESMs).


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#  Experiment characteristics  #
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The experiments run with different resolutions, thermal forcing parameters and calibrations, basal friction laws and ESM forcings.  As described in Lipscomb et al. (2021), the standard experiments are run at 4km resolution with the DIVA approximation of the Stokes stress balance and with a basal friction power law (p = 0).  Various sensitivity experiments change the grid resolution, Stokes approximation, or basal friction law.  Other sensitivity experiments prescribe ice-shelf collapse.
Grid resolution: 8km, 4km, 2km
Melt parameterization: local, nonlocal, nonlocal-slope. Nonlocal-slope is denoted as “slope” in the archive.
Melt calibration: MeanAnt, PIGL
Basal friction: p = 0 (power law), p = 0.5 (Schoof law), p = 1 (Schoof law)
Stokes approximation: DIVA, Blatter-Pattyn
ESM forcing: CCSM4, CESM2, HadGEM2, MIROC, NorESM, UKESM


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#   Forcing folder organization   #
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There are two kinds of forcing, ocean thermal forcing and ice-shelf collapse.  The ocean thermal forcing is computed as a background climatology added to annual ESM anomalies (the anomalies are computed with reference to years 1941–1960).  The ice-shelf collapse files contain annual retreat masks. 

1. Ocean thermal forcing
Organized as: resolution / ESM_file
Available resolutions: 8km, 4km, 2km
The files at 4km and 2km were interpolated from those at 8km. 
Figure references: 9, 10

2. Ice-shelf collapse
Organized as: resolution / ESM_file
Available resolutions: 4km (interpolated from forcing originally at 8km).


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#   Spinup folder organization   #
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Contains three initial-condition files and four folders.  The folder names correspond to the various spin-up experiments.
Note: Many forward experiments can start from the same spin-up.  This information will be specified in the next section. 

The initial-condition file, based on observations, is the same for all spin-ups at a given resolution and is named “ISMIP6_Antarctica_4km.bedmachine2.ice_domain_mask.nc” (or similarly for other resolutions).

For each folder, the paths are organized as:
Experiment / resolution / melt_parameterization / melt_calibration /

Each folder at the base of the path structure (e.g., “Spinup/DIVA_p_00/4km/nonlocal/meanant”) contains four kinds of files:
1. One or two config files (one used at initialization and one at restart): “ISMIP6_4km.config” and “ISMIP6_4km.config.restart” (or similarly for other resolutions)
2. A history file containing one time slice corresponding to the end of the spin-up and named “out_ISMIP6_Antarctica_4km.nc”  
3. A restart file (used to initialize forward runs), containing one time slice corresponding to the end of the spin-up and named “ISMIP6_Antarctica_4km.1950_init.nc”
4. A time series file containing scalar output with a frequency of 10 years spanning the entire spin-up, named “out_ISMIP6_Antarctica_4km.scalars.nc”

Note: in what follows, "Figure references" refers to the figure in the paper where the information in the forder is used. 


1. DIVA_p_00
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 8km, 4km, 2km
Parameterization: local, nonlocal, slope (only nonlocal and slope at 2 km)
Calibration: MeanAnt, PIGL
Figure references: 2, 3, 4, 5, 6, 12, 14, 16, 18, 20

2. DIVA_p_05
Stokes approximation: DIVA
Basal friction: p = 0.5
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Figure references: None

3. DIVA_p_10
Stokes approximation: DIVA
Basal friction: p = 1
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Figure references: 20, 22

4. Blatter-Pattyn
Stokes approximation: Blatter-Pattyn
Basal friction: p = 0
Resolution: 8km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Figure references: 16


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#   Forward folder organization   #
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Contains two main folders, one for the control runs (without ESM thermal forcing anomalies) and one for the experiments with ESM thermal forcing anomalies.

The Control folder has the same organization as the Spinup folder:
Experiment / resolution / melt_parameterization / melt_calibration /

For the runs with ESM forcing the paths are organized as:
Experiment /resolution / ESM / melt_parameterization / melt_calibration /

Each folder at the base of the path structure (e.g., “Forward/DIVA_p_00/4km/cesm2/nonlocal/meanant”) contains four files: 

1. A config file, “ismip6.config”
2. A history file containing one time slice corresponding to year 2500 and named “out_ISMIP6_Antarctica_4km.nc” (or similarly at other resolutions) 
3. A restart file, containing one time slice corresponding to the last saved time slice (could vary) and named “ISMIP6_Antarctica_4km.restart.nc”
4. A time series file containing scalar output with a frequency of 1 year spanning the entire experiment, named “out_ISMIP6_Antarctica_4km.scalars.nc”

1. DIVA_p_00
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 8km, 4km, 2km
Parameterization: local, nonlocal, slope (only nonlocal and slope at 2 km)
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_00
Figure references: 11, 12, 13, 14, 15, 16, 17, 18, 19, 20

2. DIVA_p_05
Stokes approximation: DIVA
Basal friction: p = 0.5
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_05
Figure references: 19

3. DIVA_p_10
Stokes approximation: DIVA
Basal friction: p = 1
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_10
Figure references: 19, 20

4. DIVA_p_05_dTb0
Stokes approximation: DIVA
Basal friction: p = 0.5
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_05
Figure references: None
Note: This experiment is like DIVA_p_05, except that dT_sector = 0.0 for the Amundsen sector.

5. DIVA_p_10_dTb0
Stokes approximation: DIVA
Basal friction: p = 1
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_10
Figure references: 21, 22, 23
Note: This experiment is like DIVA_p_10, except that dT_sector = 0.0 for the Amundsen sector.

6. Blatter-Pattyn
Stokes approximation: Blatter-Pattyn
Basal friction: p = 0
Resolution: 8km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: Blatter-Pattyn
Figure references: 15, 16

7. DIVA_dT1
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_00
Figure references: 7
Note: This experiment is like the control experiment for DIVA_p_00, except that a uniform thermal forcing anomaly of 1oC is applied beneath floating ice.

8. DIVA_dT2
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_00
Figure references: 8
Note: This experiment is like the control experiment for DIVA_p_00, except that a uniform thermal forcing anomaly of 2oC is applied beneath floating ice.

9. IceCollapse
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_0
Figure references: 17
Note: This experiment is like DIVA_p_00, except that ice shelves are removed using ISMIP6 shelf-collapse masks.

10. DIVA_2100_RemoveShelf
Stokes approximation: DIVA
Basal friction: p = 0
Resolution: 4km
Parameterization: nonlocal, slope
Calibration: MeanAnt, PIGL
Spin-up folder: DIVA_p_00
Figure references: 17, 18
Note: This experiment is like DIVA_p_00, except that small ice shelves are removed abruptly in year 2100. The file “ISMIP6_Antarctica_4km.2100_init.nc” is added in these directories as it is used as the initial profile for the small shelf collapse runs. 

Note: Of these ten experiments, the Ctrl directory contains only the experiments DIVA_p_00, DIVA_p_05, DIVA_p_10, and Blatter-Pattyn.