Sea-Ice in ROMS
Kate Hedstrom, UAFPaul Budgell, Bergen
Enrique Curchitser, LDEO
Outline
• Equations– Dynamics– Thermodynamics
• Code– cppdefs.h– SeaIce directory– ice.in
• Papers and plans
Dynamics
• Momentum equations:
• Viscous-plastic term:
More Dynamics
• Ice strength:
• Rearrange VP:
• EVP version:
Solution
• Stress tensor equation is timestepped explicitly
• Young’s modulus E depends on ice thickness to keep solution close to VP solution
• Ice velocities then timestepped with air/water stresses, Coriolis
• Since it is all explicit, easy to parallelize
Thermodynamics
• Need to compute all the ice growth/melt terms shown
Advection of Tracers
• Advection uses MPDATA, advecting ice thickness, ice concentration, snow thickness, internal ice temperature
• Followed by limiter 0 <= A <= 1
More Thermodynamics
• Heat fluxes are computed through the ice and snow
• Temperature is linear in the ice• FT has an oceanic log layer
cppdefs.h
• ANA_ICE• ICESHELF• ICE_ADVECT• ICE_ALB_EC92• ICE_BULK_FLUXES• ICE_EVP• ICE_MK• ICE_MODEL
• ICE_MOMENTUM• ICE_MOM_BULK• ICE_SHOREFAST• ICE_SMOLAR• ICE_SMOOTH• ICE_THERMO• ICE_UPWIND
SeaIce Directory• Boundary conditions– aibc.F, hibc.F, hsnbc.F,
sfwatbc.F, sig11bc.F, sig12bc.F, sig22bc.F, tibc.F, uibc.F, vibc.F
• ice.F• ice_advect.F
– ice_smolar.h
• ice_thermo.F– ice_mk.h
• EVP rheology– ice_evp.F,
ice_evp_sig.F, ice_elastic.F
• ice_frazil.F• ice_limit.F, ice_smoother.F
• ice_spdiw.F, ice_vbc.F
ice.in
• Lice - logical for ice• dtice - same as ocean dt• nevp - number of EVP iterations per step
• rhoice, rho_air, rhosnow_dry, rhoshow_wet - various densities
• cdiw, cdai - drag coefficients• gamma2 - slipperiness parameter• pstar, astren - strength parameters
ice.in
• zetamax, zetamin - min/max for ice viscosity
• ellip_sq, alphai - ellipticity of yield curve squared
• min_h, min_a, max_a - ice limiters for thickness and concentration
• stressang• ice_emiss, spec_heat_air, trans_coeff, sublim_latent_heat - various thermodynamic parameters
Papers
• Hunke and Dukowicz, An Elastic-Viscous-Plastic Model for Sea Ice Dynamics, JPO, 27, 1849-1867 (1997)
• Hunke, Viscous-Plastic Sea Ice Dynamics with the EVP Model: Linearization Issues, JCP, 170, 18-38 (2001)
• Mellor and Kantha, An Ice-Ocean Coupled Model, JGR, 94, 10,937-10,954 (1989)
• Hakkinen and Mellor, Modeling the Seasonal Variability of a Coupled Arctic Ice-Ocean System, JGR, 97, 20,285-20,304 (1992)
Plans
• Modeling the Bering Sea at 4 km resolution
• Replacing Mellor-Kantha with CICE 3.1 (Wang and Zhang)– Multicategory and multilevel for interal ice
temperatures– They need that for the Arctic