ACCIMA ROMS issuesACCIMA ROMS issues

Mike DinnimanMike DinnimanJohn KlinckJohn Klinck

Center for Coastal Physical Center for Coastal Physical OceanographyOceanography

Old Dominion UniversityOld Dominion University

December 16, 2011December 16, 2011

OutlineOutline

• Test ocean only circum-Antarctic simulation

• Code version?

• Grid questions

• Things to add

• Ocean analysis metrics

Ocean Test SimulationOcean Test Simulation• ROMS: ~10 km horizontal resolution ROMS: ~10 km horizontal resolution

(800x800) on a polar stereographic grid, 32 (800x800) on a polar stereographic grid, 32 vertical levels vertical levels

• Ice shelves (mechanical and thermodynamic)Ice shelves (mechanical and thermodynamic)

• Initial Initial θθ and S from 18-km ECCO2 and S from 18-km ECCO2

• Lateral boundary conditions from ECCO2 (Lateral boundary conditions from ECCO2 (θθ, , S) and SODA (Ū and SSH)S) and SODA (Ū and SSH)

• ECMWF-Interim daily winds for 2010ECMWF-Interim daily winds for 2010

• No sea ice, no tides, no surface heat or fresh No sea ice, no tides, no surface heat or fresh water fluxes in open ocean, simple relaxation water fluxes in open ocean, simple relaxation of surface of surface θθ (30d) and S (120d) (30d) and S (120d)

Ocean Test Simulation (cont.)Ocean Test Simulation (cont.)• Timmermann et al. bathymetry (1 min Timmermann et al. bathymetry (1 min

resolution bedrock and ice surfaces)resolution bedrock and ice surfaces)

• Grid is not large enough to include all the Grid is not large enough to include all the ACC fronts (does cover maximum sea ice ACC fronts (does cover maximum sea ice extent)extent)

• 1 year simulation takes 71 hours on 32 cores 1 year simulation takes 71 hours on 32 cores (should scale well: 31 hours on 64 cores)(should scale well: 31 hours on 64 cores)

• Is ocean “only” run going to be Is ocean “only” run going to be coupled w/ LANL CICE (i.e. should we wait for coupled w/ LANL CICE (i.e. should we wait for the coupling)? If not, do an ocean “only” run the coupling)? If not, do an ocean “only” run w/ built in Budgell sea ice?w/ built in Budgell sea ice?

ACC Fronts (STF, SAF, PF, SACCF, SB) and Test

Domain

5 day averages of model sea surface height

5 day averages of model sea surface temperature

ROMS Version?ROMS Version?

• Test model is modified v3.4Test model is modified v3.4

• Latest version with Budgell (not LANL CICE) Latest version with Budgell (not LANL CICE) sea ice and ice shelf code is modified v3.5 sea ice and ice shelf code is modified v3.5 (Kate Hedström’s “semi-official” branch)(Kate Hedström’s “semi-official” branch)

• Latest “official” version from Rutgers is v3.6 Latest “official” version from Rutgers is v3.6 (does not include ice shelves or sea ice)(does not include ice shelves or sea ice)

• Related: Are we still setting up a CVS Repository?Related: Are we still setting up a CVS Repository?

ROMS grid?ROMS grid?

• What horizontal resolution? Proposal said What horizontal resolution? Proposal said we would start with 10 km. Dream would we would start with 10 km. Dream would be eddy resolving on shelf (1.5 km?)be eddy resolving on shelf (1.5 km?)

• Doesn’t have to cover same area as the Doesn’t have to cover same area as the atmosphere (should be same grid for sea atmosphere (should be same grid for sea ice), but that would be nice. If not, what ice), but that would be nice. If not, what gets used for forcing? gets used for forcing?

• What lateral extent? We would like to at What lateral extent? We would like to at least cover out to the Subantarctic Front least cover out to the Subantarctic Front (45% increase in grid points from present)(45% increase in grid points from present)

ROMS things to addROMS things to add • Tides (said we would in the proposal)?Tides (said we would in the proposal)?

• Updated equation of state (Jackett and Updated equation of state (Jackett and McDougall, 2006: valid down to -10 °C)McDougall, 2006: valid down to -10 °C)

• Ice shelf thickness respond to basal melt/freeze (if Ice shelf thickness respond to basal melt/freeze (if no lateral movement or calving, this is easy)no lateral movement or calving, this is easy)

• Frazil ice? (available but computationally Frazil ice? (available but computationally expensive)expensive)

• Artificial tracers (e.g. dyes explicitly representing Artificial tracers (e.g. dyes explicitly representing CDW, ISW, AABW)CDW, ISW, AABW)

(courtesy Scott Springer, ESR)

Dye concentration at depth (model level 13) vs. observations showing presence or absence of MCDW

ROMS metrics (with constraints)ROMS metrics (with constraints) • ACC transport (observations and ocean reanalyses)ACC transport (observations and ocean reanalyses)

• Frontal positions (in-situ observations and altimetry)Frontal positions (in-situ observations and altimetry)

• Water mass census (ARGO floats, obs climatologies Water mass census (ARGO floats, obs climatologies and reanalyses)and reanalyses)

• Selected cross sections (esp. repeat sections like Selected cross sections (esp. repeat sections like Drake Passage; also WOCE lines, ANSLOPE, Drake Passage; also WOCE lines, ANSLOPE, SOGLOBEC)SOGLOBEC)

• SST and sea ice extent and drift (satellite obs)SST and sea ice extent and drift (satellite obs)

• SSH variability (altimetry)SSH variability (altimetry)

• Ice shelf basal melt estimatesIce shelf basal melt estimates

ROMS metrics (less sure about ROMS metrics (less sure about constraints)constraints)

• Heat flux across the shelf breakHeat flux across the shelf break

• CDW volume flux across the shelf breakCDW volume flux across the shelf break

• Freshwater content in the ocean mixed layerFreshwater content in the ocean mixed layer

• Sea ice production in coastal polynyasSea ice production in coastal polynyas

• AABW formationAABW formation

DICE

IICE

DICE+

Clim

300m mean salinity

Difference mostly due to higher friction velocities under ice shelf, but also some effect from changes in water masses on open shelf

(courtesy Scott Springer, ESR)

Ice Shelf ModelingIce Shelf Modeling

• Ice Shelf does not change in time in modelIce Shelf does not change in time in model

• Three equation viscous sub-layer model Three equation viscous sub-layer model for heat and salt fluxes (Holland and for heat and salt fluxes (Holland and Jenkins, 1999)Jenkins, 1999)– Conservation of HeatConservation of Heat– Conservation of SaltConservation of Salt– Freezing point of sea water (function of Freezing point of sea water (function of

pressure and salinity)pressure and salinity)

• PGF calculation assumes the ice shelf has PGF calculation assumes the ice shelf has no flexural rigidity and pressure at the no flexural rigidity and pressure at the base comes from the floating icebase comes from the floating ice