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A Global Hindcast of Ice and Ocean Conditions for 1958-2004

IMR. A Global Hindcast of Ice and Ocean Conditions for 1958-2004 (with a Focus on the North Atlantic and Arctic) W. Paul Budgell and Vidar S. Lien Institute of Marine Research and Bjerknes Centre for Climate Research Bergen, Norway Alcal á de Henares November 6-8, 2006. IMR.

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A Global Hindcast of Ice and Ocean Conditions for 1958-2004

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  1. IMR A Global Hindcast of Ice and Ocean Conditions for 1958-2004 (with a Focus on the North Atlantic and Arctic) W. Paul Budgell and Vidar S. Lien Institute of Marine Research and Bjerknes Centre for Climate Research Bergen, Norway Alcalá de Henares November 6-8, 2006

  2. IMR Outline of Talk: • Background • Description of ice-ocean model • Model set-up • Preliminary simulation results • Conclusions

  3. IMR Background • Performing global ice-ocean forecast for 1958-2004 • Archived hindcast results used to run ecosystem model off-line and generate time series of biophysical/indicators for fisheries-climate studies • Global to provide dynamically-consistent fields for boundary forcing of regional models

  4. IMR Ocean Model Component (ROMS v. 3.0) • 3rd-order upwind-biased horizontal advection • Piece-wise parabolic splines in vertical, spline vertical advection, spline Jacobian baroclinic pressure gradient at topography • LMD mixing with bottom PBL extension • Global tides with tidal potential and SAL correction • Atmospheric pressure gradient forcing

  5. IMR Ice Dynamics • Ice dynamics based upon the elastic-viscous-plastic (EVP) rheology of Hunke and Dukowicz (1997), Hunke (2001) and Hunke and Dukowicz (2002) • Under low deformation (rigid behaviour), the singularity is regularized by elastic waves • response is very similar to viscous-plastic models in typical Arctic pack ice conditions • Numerical behaviour improved significantly by applying linearization of the viscosities at every EVP time step • The EVP model parallelizes very efficiently under both OpenMP And MPI

  6. IMR Ice Thermodynamics Ice thermodynamics are based upon those of Mellor and Kantha (1989) and Häkkinen and Mellor (1992) Main features include: • Three-level, single layer ice; single snow layer • Molecular sublayer under ice; Prandtl-type ice-ocean boundary layer • Surface melt ponds; enthalpy conservation • Forcing by short and long-wave radiation, sensible and latent heat flux • Tight coupling to ocean surface boundary layer

  7. IMR Model Grid Every 10th point in i,j directions plotted

  8. IMR Model Grid Size

  9. IMR Model Set-up • Horizontal resolution of 8.9 to 105 km, average of 20 km in N. Atlantic and Arctic on a stretched spherical grid with Mercator projection • 35 levels in the vertical, stretched for enhanced resolution in the surface mixed layer, Θs=5.0, Θb=0.4, hmin=30m

  10. Initial Conditions and Forcing • Initial condition in Jan.1, 1958 from Jan.1, 2001 from NERSC MICOM global hindcast from 1948-2001, then 2 years of forcing with CORE corrected normal year • CORE (Common Ocean-ice Reference Experiment) data set used for forcing; surface heat and momentum fluxes computed using COARDS 3.0 bulk flux algorithms in ROMS • Restoration of sea surface salinity to climatology with 90 day e-folding time IMR

  11. IMR Spin-Up Still Required!

  12. IMR Results – SST - March Observed Climatology March (Pathfinder) Model results March, 2004

  13. IMR Results – SST - September Observed Climatology September (Pathfinder) Model results September, 2004

  14. IMR Daily Mean Ice Concentration March 20, 1980 Observed (SMM/R) Modelled

  15. IMR Daily Mean Ice Concentration Sept.19, 1980 Observed (SMM/R) Modelled

  16. IMR Modelled Monthly Mean Sea Ice Thickness (m) March, 1980 September, 1980

  17. Preliminary Results - Sections

  18. IMR Northward Velocity at 66ºN and the NAO High NAO LowNAO Low NAO

  19. Average circulation at 50m depth 1963-1966 Low NAO 1972-1976 High NAO W branch of Atl. inflow stronger in years with high NAO-index (i.e. more SW winds)

  20. IMR Section at the Barents Opening 50-200m average from 71°30’N to 73°30’N Atlantic Inflow (Mooring “sampling”) Observed (AW net, 1997-2001): 1.5 Sv Modelled (AW net, 1997-2001): 1.8 Sv

  21. IMR Bering Strait Transport to the Arctic Modelled: 1.15 Sv Woodgate: 0.8 Sv Roach: 0.83 Sv Clement: 0.65 Sv (Modelled)

  22. IMR Southward Labrador Current Transport Modelled DSO Transport = 13-14 Sv Observed DSO Trans (Fischer et al., 2004) 13.8 Sv. Modelled LSW Trans = ~11-12 Sv Obs LSW Trans (Fischer et al., 2004) =11.4 Sv

  23. IMR Fram Strait Transport Modelled Northward Transport = 9.0 Sv Observed Northward Transport = 9 +/- 2 Sv (Schauer et al., 2004) Modelled Southward Transport = 12.9 Sv Observed Southward Transport = 13 +/- 2 Sv

  24. IMR East Greenland Current Transport Modelled Average Southward Trans = 25.1 Sv Observed Average Southward Trans = 21 +/- 3 Sv (Woodgate et al., 1999) Net Atlantic Water Southward Trans = 8.8 Sv Net Atlantic Water Southward Trans = 8 +/- 1 Sv (Woodgate et al., 1999)

  25. IMR Animations of Annual Variability Results are shown from the first year of a global simulation starting in 2001 using NCEP flux forcing Initialized from coarse MICOM hindcast of 1948-2000 SSTIce Concentration

  26. IMR Nesting from Global to Barents: SST

  27. IMR Nesting from Global to Barents: Surface Currents

  28. IMR Storfjorden Mesoscale Ice-Ocean Interaction

  29. IMR Summary and Conclusions • The first pass of a global ice-ocean hindcast has been completed for 1958-2004 and data are archived as 3-day and monthly means • The results are not spun up in the deep ocean until the early 1980’s • The results generally look reasonable and time series are being analyzed for interannual & decadal-scale variability • Archived hindcast fields are being used for nesting of regional models and in off-line IBM simulations of zooplankton and fish larvae simulations, and off-line ecosystem simulations

  30. IMR Future Work • Problems with anomalous cold patches off Argentina and in the central North Atlantic – probably due to errors in w-computation (pers.comm. Daniel Deacu, Memorial Univ., NL, Canada) • Will repeat the hindcast from Jan., 1958 initialized from Jan., 1996; SSS restoration will be replaced with spectral (12-month and long-term mean) correction of surface salt flux based on archived salinity restoration flux time series from the first run • “Potential vorticity barrier” inhibits Atlantic inflow to the Nordic Seas; need to find a suitable parameterization

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