Landice Modes¶

ModelE (e3/landice branch) can run with three approaches to landice (ice sheets): Classic, Stieglitz or Coupled:

Classic (default): How ModelE has been running by default since the 1980’s. The top 3m of an ice sheet are modeled using a simple 2-layer model built into ModelE [Alexander et al 2018]. If ice accumulates over 3m, it is “pushed down” into the mdwnimp and edwnimp variables; if it melts to less than 3m, it is “pulled up” from the same.
Stieglitz: The 2-layer model was replaced with a Lynch-Stieglitz model, with 5 layers by default. Otherwise, the “push down” and “pull up” behavior remains unchanged.
Coupled: The Lynch-Stieglitz model is used for snow/firn, but it is placed on top of a dynamic ice sheet. The ice sheet is modeled on a separate grid with a separate code (eg PISM), and IceBin is used to couple between the two. In areas of the globe that are covered in ice but do not have a dynamic ice model, this mode is the same as Stiegtliz.

Instructions on using these different modes follow:

Classic Snow/Firn Model¶

The classic snow/firn model is enabled by default. Nothing needs to be done to the rundeck to enable this. Note that Classic can be used with or without elevation classes.

Note

modele_control is required for: #. Code generation to dump constants

File Format: TOPO¶

The TOPO file provides land surface fraction and elevation class information to ModelE; see here <http://twoway.readthedocs.io/en/latest/topo.html> for more information. The number of elevation classes is picked up automatically; if a classic TOPO file without elevation class information is used, then ModelE will rever to running without elevation classes.

File Format: GIC¶

Variables snowli and tlandi in the GIC file may have an extra nhc (elevation class) dimension, but they don’t have to. If they do, the nhc from GIC must match that from TOPO. Otherwise, the values of snowli and tlandi are repeated for every elevation class within each grid cell.

Stieglitz Snow/Firn Model¶

The Stieglitz snow/firn model may be enabled by making the following changes to the ModelE rundeck:

Add lipluggable to the Components section of the rundeck.
Build with modele_control <https://github.com/citibeth/modele-control>. If not, one must also add to the Preprocessor Options section of the rundeck:

The following rundeck parameters are now enabled. See LISnowParams.F90 for documentation:

lisnow_target_depth
lisnow_rho_fresh_snow
lisnow_rho_snow_firn_cutoff
lisnow_max_fract_water
lisnow_epsilon
lisnow_min_snow_thickness
lisnow_min_fract_cover
lisnow_dump_forcing
lisnow_percolate_nl

File Format: TOPO¶

The TOPO file is the same for Stieglitz vs. Classic ice model. As with Classic, ModelE infers elevation classes for a run from the TOPO file.

File Format: GIC¶

Stieglitz has a different internal state from the classic ice model. Therefore, the variables it reads form GIC are different. The variables snowli and tlandi are no longer needed. They are replaced by (NetCDF index ordering):

dz(nhc,j,i,nlice) [m]: Depth of each layer
wsn(nhc,j,i,nlice) [kg m-2]: Mass of each layer
hsn(nhc,j,i,nlice) [J m-2]: Enthalpy of each layer
trsn(nhc,j,i,nlice,ntm) (OPTIONAL) Tracer state

Note

Specific enthalpy [J kg-1] for hsn would have been more convenient than enthalpy because it corresponds directly to temperature. That change might happen in the future.
As with the Classic model, the nhc (elevation class) dimension is optional. If it is missing, values for these variables provided by GIC are read into all elevation classes.

Coupled Mode¶

(Instructions not yet tested)

Do everything needed for Stieglitz Model above, plus:

When setting up the Spack environment, make sure that the variants icebin+coupler+modele+pism and modele+icebin are used.
Spin up a PISM. Note the name of its state file <pism-state>
Build with modele-control.
Add #define USE_ICEBIN to the defines section. This enables coupled mode, but does not turn it on.
Set LIMODE=twoway in rundeck.
Createa ModelE run directory:
```
ectl setup <run-dir> ...
```
Somewhere do git clone https://github.com/citibeth/twoway.git
In your ModelE run directory, do:
```
cd <modele-run-dir>
# 20km grid
python3 <twoway>/topo/modele_pism_inputs.py --out input --pism <pism-state>
cp input/icebin.cdl config
```
Try python3 <twoway>/topo/modele_pism_inputs.py --help for further details if you need something other than the SeaRise-style 20km grid. (TODO: This program should really determine the grind from the PISM state file)
Edit config/icebin.cdl as appropriate.

(Where is this found? How do I create one????)

netcdf OZ1QX1N.BS1 { dimensions:

lono = 288 ; lato = 180 ;

variables:

float lono(lono) ;: lono:units = “degrees_east” ;
float lato(lato) ;: lato:units = “degrees_north” ;

float focean(lato, lono) ; float zatmo(lato, lono) ; float zocean(lato, lono) ;

}

Need to create TOPO_OC file for ModelE input from topoo.nc:: 1. Convert FOCEAN, ZATMO and dZOCEAN into focean, zatmo and zocean. 2.
Add to rundeck:: TOPO

Andd TOPOO rundeck parameter!!!

Setting Up an Uncoupled Lynch-Stieglitz Run¶

Step-by-step instructions.

Use the twoway-gibbs or similar Spack environment:

source ~/spack7/environments/twoway-gibbs/loads-x

Make sure the following Git repos are checked out into a top-level git superdirectory; which will be called ~/git below. They can be read-only.
- modelE
- twoway
Create a new project directory. Multiple runs will live in this.
```
mkdir myproject
cd myproject
echo >ectl.conf
cd project
```
Create a new run with a new rundeck. The rundeck can be an existing rundeck, or taken straight from the templates. Eg:
```
ectl setup -rd E6F40.R --src ~/git/modelE test1 --nobuild
```
If the rundeck uses non-Stieglitz GIC file (the default for templates), create a new Stieglitz-enabled GIC file:
```
python3 ~/git/twoway/stieglitz/gic2stieglitz.py -d test1 GIC -o inputs/
```
Use your favorite editor on test1/rundeck.R to make the following changes:
1. Use the new GIC file created above:
2. Use a an EC-enabled TOPO file (generated by ~/git/twoway/topo/makefile).

Setting Up a Coupled Run¶

Step-by-step instructions.

Use the twoway-gibbs or similar Spack environment:

source ~/spack7/environments/twoway-gibbs/loads-x

Make sure the following Git repos are checked out into a top-level git superdirectory; which will be called ~/git below. They can be read-only.
- modelE
- twoway
- pism
Create a new project directory. Multiple runs will live in this.
```
mkdir myproject
cd myproject
echo >ectl.conf
```

Create a spun-up PISM. Normally, this would be part of the project directory, and be used by multiple runs.

# cd myprojet
cp -r ~/git/pism/examples/std-greenland .
cd std-greenland
./preprocess.sh
nproc=12   # Or however many cores you have on your machine
nice ./spinup.sh $nproc const 1000 20 sia g20km_10ka.nc

Create a new run with a new rundeck. The rundeck can be an existing rundeck, or taken straight from the templates. Eg:
```
ectl setup -rd E6F40.R --src ~/git/modelE-e3landice test1 --nobuild
```
If the rundeck uses non-Stieglitz GIC file (the default for templates), create a new Stieglitz-enabled GIC file:
```
python3 ~/git/twoway/stieglitz/gic2stieglitz.py -d test1 GIC -o inputs/
```

Create merged TOPO and GIC files

python3 ~/git/twoway/topo/modele_pism_inputs.py --pism std-greenland/g20km_10ka.nc --grids grids --gic GIC.144X90.DEC01.1.ext_1.nc --run test1

Edit test1/rundeck.R, make the following changes:
1. Add libpluggable to the Components section of the rundeck (test1/rundeck.R). This will do the following:
  1. Builds the Fortran code inside <modelE>/model/lipluggable.
  2. Adds the preprocessor symbol LIPLUGGABLE to the rundeck_opts.h file (done inside the modele-control.pyar CMake-based build).
2. Add LI_TWOWAY setting in the rundeck &&PARAMETERES section of the rundeck: .. code-block:
```
LI_TWOWAY=1
```
3. Use the new GIC file created above:
4. Use the new TOPO file created above:
NOTE: The icebin configuration file is in test1/config/icebin.cdl
Re-run setup, to make sure