Merge #403

403: Bring back Semtner Sea Ice r=LenkaNovak a=LenkaNovak



Co-authored-by: LenkaNovak <[email protected]>

.buildkite/pipeline.yml

@@ -140,7 +140,6 @@ steps:
         agents:
           slurm_mem: 20GB
 
-      # Test: non-monotonous remapping for land mask
       - label: "Slabplanet: non-monotonous surface remap"
         key: "slabplanet_non-monotonous"
         command: "julia --color=yes --project=experiments/AMIP/modular/ experiments/AMIP/modular/coupler_driver_modular.jl --config_file $CONFIG_PATH/slabplanet_nonmono.yml"
@@ -168,6 +167,13 @@ steps:
         agents:
           slurm_mem: 20GB
 
+      - label: "Slabplanet: eisenman sea ice"
+        key: "slabplanet_eisenman"
+        command: "julia --color=yes --project=experiments/AMIP/modular/ experiments/AMIP/modular/coupler_driver_modular.jl --config_file $CONFIG_PATH/slabplanet_eisenman.yml"
+        artifact_paths: "experiments/AMIP/modular/output/slabplanet_eisenman/slabplanet_eisenman_artifacts/*"
+        agents:
+          slurm_mem: 20GB
+
       # AMIP
 
       # ...

config/model_configs/interactive_debug.yml

@@ -4,7 +4,7 @@ rad: "gray"
 energy_check: true
 mode_name: "slabplanet"
 t_end: "10days"
-dt_save_to_sol: "2days"
+dt_save_to_sol: "0.5days"
 dt_cpl: 400
 dt: "400secs"
 mono_surface: true

config/model_configs/slabplanet_eisenman.yml

@@ -0,0 +1,17 @@
+run_name: "slabplanet_eisenman"
+surface_setup: "PrescribedSurface"
+moist: "equil"
+vert_diff: "true"
+rad: "gray"
+energy_check: true
+mode_name: "slabplanet_eisenman"
+t_end: "10days"
+dt_save_to_sol: "9days"
+dt_cpl: 200
+dt: "200secs"
+mono_surface: true
+h_elem: 6
+precip_model: "0M"
+anim: true
+apply_limiter: false
+job_id: "slabplanet_eisenman"

experiments/AMIP/modular/components/ocean/eisenman_seaice.md

@@ -0,0 +1,60 @@
+# Eisenman-Zhang Model
+Thermodynamic 0-layer model, based on the Semtner 1979 model and later refined by
+Eisenman & Wettlaufer (2009) and Zhang et al. (2021).
+
+There are three prognostic variables, the height of ice (`h_i`), the ocean mixed layer depth (`T_ml`) and the surface air temperature (`T_s`).
+
+## Formulation
+In ice-covered conditions:
+$$
+L_i \frac{dh_i}{dt} = F_{atm} - F_{base} - Q
+$$
+with the density-weighted latent heat of fusion, $L_i=3 \times 10^8$ J m$^{-3}$, and where the (upward-pointing) flux into the atmosphere is
+$$
+F_{atm} = F_{rad} + F_{SH} + F_{LH}
+$$
+where $F\_{rad}$ is the net radiative flux, $F_{SH}$ is the sensible heat flux and $F_{LH}$ is the latent heat flux.
+
+The basal flux is
+$$
+F_{base} = F_0(T_{ml} - T_{melt})
+$$
+where $T_{melt} = 273.16$ K is the freezing temperature, and the basal heat coefficient $F_0 = 120$ W m$^{-2}$ K$^{-1}$.
+
+The lateral oceanic heat flux is parameterized as a prescribed $Q$-flux. With $F_{base} = T_{ml}^{t+1} = T_{melt}$ when ice is present, and zero $Q$-flux in the default setup, the base flux is zero in that case.
+
+The surface temperature of the ice-covered surface is solved by balancing $F_{atm}(T_s)$ and the conductive heat flux through the ice slab, $F_{ice}$:
+$$
+F_{atm} = F_{ice} = k_i \frac{T_{melt} - T_s}{h_i}
+$$
+where $k_i = 2$ W m$^{-2}$ K$^{-1}$ is the thermal conductivity of ice.
+Currently the solve is implemented as one Newton iteration (sufficient for the current spatial and temporal resolution - see Semtner, 1976):
+$$
+T_s^{t+1} = T_s + \frac{F}{dF /d T_s}  = T_s^{t} + \frac{- F_{atm}^t + F_{ice}^{t+1}}{k_i/h_i^{t+1} + d F_{atm}^t / d T_s^t}
+$$
+where $h_i^{t+1}$ is the updated $h^i$ from the previous section, and $d F_{atm}^t / d T_s^t$ needs to be estimated using $T_s + \delta T$.
+
+### Warm surface
+In ice-free conditions, the ocean temperature $T_{ml}$ assumes the standard slab model representation:
+$$
+\rho_w c_w h_{ml}\frac{dT_{ml}}{dt} = - F_{atm}
+$$
+In this case, $T_s^{t+1} = T_{ml}^{t+1}$
+
+### Frazil ice formation
+The frazil ice formation rate is parameterized as a function of the mixed layer temperature. It occurs when the newly calculated ocean temperature $T_{ml}^{t+1} < T_{melt}$. Since the mixed layer is not allowed to cool below $T_{melt}$, the energy deficit is used to grow ice:
+$$
+\frac{dh_i}{dt} = \Delta h_i^{t+1} + \frac{\Delta T \rho_w c_w h_{ml}}{L_i \Delta t}
+$$
+with $\Delta T =  T_{melt} - T_{ml}^{t+1} $.
+
+### Transition to ice-free conditions
+- If the updated $h_i^{t+1} < 0$ from a non-zero $h_i^t$, the ice height is set to zero and the surplus energy warms the mixed layer.
+
+## Potential extensions
+- add area `ice_area_fraction` adjustment (e.g., assuming a minimal thickness of sea ice, below which the grid area becomes part ice and part ocean)
+
+# References
+- [Semtner 1976](https://journals.ametsoc.org/view/journals/phoc/6/3/1520-0485_1976_006_0379_amfttg_2_0_co_2.xml)
+- [Eisenman & Wettlaufer 2009](https://www.pnas.org/doi/full/10.1073/pnas.0806887106)
+- [Zhang et al 2021](https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021MS002671), whose implementation can be found on [GitHub](https://github.com/sally-xiyue/fms-idealized/blob/sea_ice_v1.0/exp/sea_ice/srcmods/mixed_layer.f90)