1. Sea-Ice in ROMS
Kate Hedstrom, UAF

2. Outline Equations Code Examples Future plans Dynamics Thermodynamics
cppdefs.h
SeaIce directory
ice.in
Examples
Future plans

3. Dynamics
Momentum equations:
Viscous-plastic term:

4. Ice Strength
Linear with thickness:
Quadratic with thickness:

5. More Dynamics
Rearrange VP:
EVP version:

6. 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 (ROMS tiles)

7. Thermodynamics
Need to compute all the ice growth/melt terms shown

8. Evolution of Tracers Ice volume is Ah Ice concentration is A,
Phi is tunable parameter, value depends on sign of Wao i

9. Advection of Tracers Advection uses MPDATA, upwind or full
Ice volume,
Ice concentration
Snow volume
Ice enthalpy
Etc.
Followed by limiter 0 <= A <= 1

10. More Thermodynamics Heat fluxes are computed through the ice and snow
Temperature is linear in the ice
FT has an oceanic log layer

11. Ice cppdefs.h ICE_MODEL – turn on whole seaice model
ANA_ICE – analytic initial conditions
ICESHELF – ice shelves – something else again entirely
ICE_ADVECT – turn on advection
ICE_SMOLAR
ICE_UPWIND

12. cppdefs.h ICE_MOMENTUM – turn on rheology ICE_MOM_BULK
ICE_EVP
ICE_MOM_BULK
ICE_SHOREFAST – ice slows as it fills water column
FASTICE_CLIMATOLOGY – read in locations where ice doesn’t move
ICE_STRENGTH_QUAD – quadratic ice strength as function of thickness

13. cppdefs.h ICE_THERMO – turn on thermodynamics
ICE_MK
ICE_BULK_FLUXES
OUTFLOW_MASK – turn on outflow cells
Reduces ice strength and viscosity in some cells
Cells specified in set_masks.F

14. Albedo ROMS default has shortwave radiation being net into the water
Preprocess shortwave to account for albedo
Ice/snow/melt ponds affect albedo, so incoming shortwave must be before albedo corrections
Don’t preprocess shortwave
Various options exist…

15. Albedo Options ALBEDO – needs clouds
Water only
ALBEDO_CURVE – function of latitude
ALBEDO_FILE
Ice and water
ALBEDO_CSIM
Ice only
ICE_ALB_EC92 – Ebert and Curry

16. SeaIce Directory i2d_bc.F, tibc.F, uibc.F, vibc.F ice_smolar.h
seaice.F – calls all the rest
Boundary conditions
i2d_bc.F, tibc.F, uibc.F, vibc.F
ice_advect.F – advect the ice tracers
ice_smolar.h
ice_enthalpi.F
ice_thermo.F – compute heat fluxes, melt/freeze rates
ice_mk.h

17. SeaIce Directory ice_evp.F ice_evp_sig.F ice_elastic.F EVP rheology
ice_frazil.F
Computes frazil ice formation
Called from step3d_t.F
Checks for negative ice growth and crashes ROMS if found

18. SeaIce Directory ice_limit.F ice_spdiw.F ice_vbc.F
Clamps on ice fields
ice_spdiw.F
Compute shear between ice and water in upper mixed layer
ice_vbc.F
Sets ice-water and ice-air stresses for ice momentum equation

19. SeaIce Directory ini_strengthcoef.F ice_flux_rst.F
Quadratic ice strength depends on grid spacing
Set 2D coefficient during initialization
ice_flux_rst.F
Timestepping in ROMS calls seaice before output
Seaice computes heat and momentum fluxes for ocean
To get perfect restart, we save the fluxes and use saved fluxes instead of timestepping ice in first step after restart

20. Boundary Conditions LBC options Outflow cells Nesting
Mix: clamped on inflow, gradient on outflow
Otherwise much like the ocean
Outflow cells
Specify in set_masks.F
Nesting
Offline nesting gives trouble for ice BC
Online nesting is reputed to work

21. ice.in Lice – logical for ice (ignored) dtice – ignored, uses ocean dt
nevp – number of EVP iterations per step
min_h, min_a, max_a – ice limiters for thickness and concentration
Hout, Aout for ice variables
Various things I never change – read about them in the file

22. Examples From most mature to least mature
Northeast Pacific (NEP)
Arctic
Arctic2
Cook Inlet (NWGOA)
All are ice-ocean only, just one grid

23. Northeast Pacific 11 km resolution GLOBEC, BEST, BOEM
Looking at interannual variability
First-year ice only in Bering

24. Ice Timeseries

25. Ice Concentration
Seth Danielson

26. Summary of Bering Sea
Ice extent sensitive to incoming solar radiation (including albedo)
Once tuned, the model did a good job
Spring melt is too slow (didn’t use melt pond albedo)

27. Arctic 1 Telescoping grid, 5 to 20 km Boundary at Bering Strait
20 year hindcast for BOEM
Fastice climatology

28. Ice Thickness
Satellite
Model - obs
Seth Danielson

29. Ice Concentration
Seth Danielson

30. Timeseries
Seth Danielson

31. Summary of Chukchi-Beaufort Seas
Ice too mobile, getting too thick off Siberia, too thin off Alaska
Too thin areas grow more ice, making ocean too salty
Excess ice melt in May-June, not enough later in summer
Monthly anomalies have skill except for a few problem summers (1988, 2002, 2003)

32. Arctic 2
Includes Bering Sea for looking at Bering Strait flow for NPRB
Includes Canadian archipelago
Quadratic ice strength

33. Ice Thickness

34. Northwest Gulf of Alaska
1.5 km resolution
Includes tides and WET_DRY
Fresh water from land runoff model
Try out CVMix?
For BOEM

35. Papers
Hunke and Dukowicz, An elastic-viscous-plastic model for sea ice dynamics, JPO, 27, (1997)
Hunke, Viscous-plastic sea ice dynamics with the EVP model: linearization issues, JCP, 170, (2001)
Mellor and Kantha, An ice-ocean coupled model, JGR, 94, 10,937-10,954 (1989)

36. Papers
Hakkinen and Mellor, Modeling the seasonal variability of a coupled Arctic ice-ocean system, JGR, 97, 20,285-20,304 (1992)
Overland and Pease, Modeling ice dynamics of coastal seas, JGR, 93, 15,619-15,637 (1988)
Steele, Mellor and McPhee, Role of the molecular sublayer in the melting or freezing of sea ice, JPO, 19, (1989)

37. Plans Eight years ago I wrote:
Replacing Mellor-Kantha with CICE 3.1
Now aiming for CICE 5. What does it offer?
Multiple ice categories and temperature levels
All the recent sea ice model improvements to melt ponds, rheology, drag, etc.
Still missing fast ice, embedded ice

38. Random Tips Circumpolar considerations Beyond ROMS trunk
GLOBAL_PERIODIC
grid_coords.F (floats, stations)
Beyond ROMS trunk
BIO_UMAINE, aka CoSiNE
ARCTIC in 2012 ROMS manual
BERING coming soon
With WRF