Sea-Ice in ROMS

1
Sea-Ice in ROMS

• Kate Hedstrom, UAF
• Paul Budgell, Bergen
• Enrique Curchitser, LDEO

2
Outline

• Equations
• Dynamics
• Thermodynamics
• Code
• cppdefs.h
• SeaIce directory
• ice.in
• Papers and plans

3
Dynamics

• Momentum equations
• Viscous-plastic term

4
More Dynamics

• Ice strength
• Rearrange VP
• EVP version

5
Solution

• Stress tensor equation is timestepped explicitly
• Youngs 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

6
Thermodynamics

• Need to compute all the ice growth/melt terms
  shown

7
Advection of Tracers

• Advection uses MPDATA, advecting ice thickness,
  ice concentration, snow thickness, internal ice
  temperature
• Followed by limiter 0 lt A lt 1

8
More Thermodynamics

• Heat fluxes are computed through the ice and snow
• Temperature is linear in the ice
• FT has an oceanic log layer

9
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

10
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

11
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

12
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

13
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)

14
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