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