ISMIP7 projections

Greenland and Antarctic projections for ISMIP7 run in two steps: a present-day optimization spin-up, which fits the basal friction (cb_ref) and an ocean thermal-forcing correction (tf_corr) to the observed ice thickness and writes a restart bundle, then the scenarios, which start from that bundle in 2015 and run under the ESM forcing (historical + projection) to 2300.

The par files on their own run a 10-yr forcing-only smoke test ([sim] opt = False, [spinup] time_end = 10); the scripts set the run phase and length.

Running the workflow

Run from the yelmox root, one step after the other: the scenarios read the spin-up’s last restart bundle.

scripts/ismip7/run_ismip7_greenland.sh spinup
scripts/ismip7/run_ismip7_greenland.sh scenarios

STAGE=1 creates the run folders and the SLURM script without submitting them (a dry run). The settings are at the top of each script:

Setting Greenland Antarctica
GRID GRL-8KM ANT-8KM [domain] grid_hub
GCM CESM2-WACCM CESM2-WACCM [esm] esm_name
SCENARIOS ssp126 ssp370 ssp585 ssp585 [esm] experiment
SPINUP_YEARS 15000 20000 [spinup] time_end, matches [opt] cf/tf_time_end
PROJ_END 2300 2300 [transient] time_end
OUTROOT output/ismip7_grl output/ismip7_ant spin-up in spinup/, scenarios in <ssp>/

The spin-up passes ctrl.run_step=spinup sim.relax=True sim.opt=True; each scenario passes ctrl.run_step=transient, esm.use_esm/use_hist/use_proj=True and ctrl.restart = the bundle <OUTROOT>/spinup/restart-<SPINUP_YEARS/1e3>-kyr as an absolute path (the run starts inside its own folder).

Other grids. The full input set exists for GRL-8KM, GRL-16KM and ANT-8KM, ANT-16KM, ANT-32KM (GRL-4KM lacks the ORAS4 reference ocean). The Antarctic par file reads the Earth structure of ANT-8KM ([isos] rheology_file): with another grid, also pass isos.rheology_file=isostasy_data/earth_structure/yelmo/<GRID>_GIA_HR24.nc (as opt_ant.sh does).

Short spin-ups. The spin-up relaxes the ice thickness towards the observations at first ([relax] tau1/2, until time2: 6 kyr for Greenland). A spin-up that ends before then hands the scenarios ice that the relaxation was holding in place, e.g. thin margin ice under negative SMB, which is then lost within the first years.

Tuned spin-ups

opt_grl.sh, opt_grl_ismip.sh (L. Gutierrez Gonzalez) and opt_ant.sh are 15-kyr optimization spin-ups with tuned parameters on top of the par files: the SMB taken from the ESM (comps.surface_method=climate), cb_ref started from the till friction of the bed (opt.cf_init=-1, the ytill parameters), a short relaxation (relax.time1/2 = 100), equilibrium calving, DIVA dynamics and shelf enhancement 0.5; opt_grl_ismip.sh uses von Mises calving (vm-l19) and a linear melt law. To run the scenarios from one of them, set BUNDLE in the workflow script to its last restart bundle.

Forcing

The atmosphere and ocean are a reference climatology plus ESM anomalies relative to time_esm_ref (1960–1989), applied over time_hist (1850–2014) and time_proj (2015–2300).

Greenland Antarctica
Reference atmosphere MAR v3.11 (ERA), 1961–1990 monthly RACMO2.3p2 (ERA5), 1985–2014 (time_ref)
Reference ocean ORAS4 1981–2010 annual mean meltMIP observational climatology (extrapolated)
ESM atmosphere ISMIP7 SDBN1 tas, pr, acabf, dacabfdz same, v2
ESM ocean ISMIP7 tf, so (2D) ISMIP7 thetao, so (3D, v3)
Subglacial discharge ISMIP7 sgd –
Shelf melt bmb_method = "anom", tf_method = 2 bmb_method = "quad-nl", tf_method = 1
Topography, basins ISMIP7 obs v1.3 (GrIMP surface) ISMIP7 obs v1.1 (Bedmap3)

ESMs and scenarios on Levante (ice_data/ISMIP7/<domain>/<grid>/):

ESM Greenland Antarctica
CESM2-WACCM ctrl, historical, ssp126, ssp370, ssp534-over, ssp585 historical, ssp585
MRI-ESM2-0 historical, ssp126, ssp370, ssp585 historical, ssp126, ssp370, ssp585

Output

The shared per-module files (yelmo.nc, yelmo_ts.nc, isos.nc, mshlf.nc, smbpal.nc, htopo.nc; Antarctica also yelmo_ts_APIS/WAIS/EAIS.nc) and the restart bundles restart-<kyr>-kyr/. For ISMIP7 submissions, [output] write_cmip = True writes yelmo_cmip.nc and yelmo_ts_cmip.nc every dt_cmip; write_clim = True adds the ESM forcing (esm.nc, esm_ts.nc).