Standard sea ice configuration (namelist.ice)

Sea-ice options are split between the dynamics (&ice_dyn) and thermodynamics (&ice_therm) sections. The same namelist is used whether the standard FESOM ice thermodynamics or Icepack is active (Icepack overrides the thermodynamics when enabled).

Sections of the namelist

Section &ice_dyn

  • whichEVP=0 EVP rheology flavour: 0 standard EVP, 1 modified EVP (mEVP, Kimmritz et al. 2015; tune alpha_evp/beta_evp), 2 adaptive EVP (aEVP, Kimmritz et al. 2016; tune c_aevp).

  • Pstar=30000.0, ellipse=2.0, c_pressure=20.0 yield-curve parameters controlling ice strength and ellipticity.

  • delta_min=1.0e-11 minimum strain rate used to regularise viscosities.

  • evp_rheol_steps=120 number of EVP sub-cycles per ice time step.

  • Cd_oce_ice=0.0055 ocean–ice drag coefficient.

  • ice_gamma_fct=0.5, ice_diff=0.0, theta_io=0.0 numerical stabilisation: damping factor for EVP rhs, small Laplacian diffusion and optional stress rotation angle.

  • ice_ave_steps=1 number of ocean time steps per ice dynamics step (sets sub-cycling).

  • alpha_evp=250, beta_evp=250, c_aevp=0.15 stability/tuning constants for mEVP/aEVP; use higher values on fine meshes to improve convergence.

Section &ice_therm

  • Sice=4.0 bulk ice salinity (ppt) used in freezing-point and enthalpy calculations.

  • iclasses=7, new_iclasses=.false., h_cutoff=3.0 number of ice thickness categories. When new_iclasses is true, an observationally derived distribution (Castro-Morales et al., 2013) with iclasses=15 and cutoff h_cutoff is used instead of the default even spacing.

  • h0=0.5, h0_s=0.5 lead-closing parameters (Northern/Southern Hemisphere) controlling how quickly open water is refrozen.

  • hmin=0.01, armin=0.01 minimum ice thickness and concentration to avoid numerical underflow.

  • emiss_ice=0.97, emiss_wat=0.97 longwave emissivities for snow/ice and open water.

  • albsn=0.81, albsnm=0.77, albi=0.7, albim=0.68, albw=0.1, open_water_albedo=0 shortwave albedo parameters. open_water_albedo chooses the scheme: 0 fixed albw, 1 Taylor et al., 2 Briegleb et al.

  • con=2.1656, consn=0.31 thermal conductivities of ice and snow (W/m/K).

  • snowdist=.true. distribute snowfall across thickness categories instead of a single class.

  • use_meltponds=.false. enable the built-in melt-pond parameterization; when active, melt-pond diagnostics can be written from namelist.io.

  • c_melt=0.5 concentration decay rate during melting in the standard FESOM ice thermodynamics.

  • h_ml=0.0 optional mixed-layer depth used in some simplified melt formulations (kept at 0 unless explicitly needed).