1. GFDL’s IPCC AR5 Coupled Climate Models: CM2G, CM2M, CM2.1, and CM3 Presented by Robert Hallberg But the work was done by many at NOAA/GFDL & Princeton University

2. CM2GCM2MCM2.1CM3 AtmosphereAM2.1 (L24) AM3 (L48) LandLM3 LM2LM3 Sea iceSIS OceanGOLD 1° x L63  MOM4p1 “M configuration” 1° x L50 Z* MOM4 1° x L50 Z MOM4p1 “CM2.1-like” 1° x L50 Z* ESM2G and ESM2M GFDL’s IPCC AR5 Coupled Climate Models New Models

3. Ocean Components of GFDL Coupled Climate Models CM2.1/CM3 or CM2M (MOM4.0 & 4.1) 1° res. (360x200), on tripolar grid. 50 z- or z*-coordinate vertical levels B-grid discretization Split explicit free surface ; fresh water fluxes as surface B.C. KPP mixed layer with 10 m resolution down to 200 m Full nonlinear equation of state MDPPM tracer advection (CM2M) Tracer diffusion rotated to neutral directions Marginal sea exchanges specified via “cross- land mixing” Lee et al. + Bryan-Lewis background (CM2.1) or Simmons et al. (CM2M) diapycnal diffusion Baroclinicity-dependent GM diffusivity. Anisotropic Laplacian viscosity (CM2.1) or Biharmonic Smagorinsky + Resolution scaled Laplacian viscosity (CM2M) KPP specification of interior shear-Richardson number dependent mixing 2 hour baroclinic and coupling timesteps. Partial cell topography CM2G (GOLD) 1° res. (360x210), on tripolar grid. 59 Isopycnal interior layers + 4 in ML C-grid discretization Split explicit free surface ; fresh water fluxes as surface B.C. 2-layer refined bulk mixed layer with 2 buffer layers Full nonlinear equation of state except for coordinate definition Tracer diffusion rotated to  2 surfaces Partially open faces allow explicit exchanges with marginal seas. Simmons et al. background diapycnal diffusion Visbeck variable thickness diffusivity. Biharmonic Smagorinsky + Resolution scaled Laplacian viscosity. Jackson et al (2008) shear-Richardson number dependent mixing. 1 hour baroclinic timestep, 2 hour tracer & coupling timesteps Continuously variable topography

4. Pacific 2000 dbar Potential Density Surfaces from CM2G

6. 100-Year Annual Mean SST Errors CM2G 1.18°C RMS CM2M 1.02°C RMS CM2.1 1.17°C RMS CM3 1.01°C RMS

7. 100-Year Annual Mean SSS Errors CM2G 0.93 PSU RMS CM2M 1.05 PSU RMS CM2.1 0.87 PSU RMS CM3 0.89 PSU RMS

8. BROAD METRICS OF THE INTERIOR OCEAN STRUCTURE

9. Global Mean Temperature Bias & RMS Errors, ~190 Years CM3 CM2G (GOLD) CM2M CM3 CM2G (GOLD) CM2M CM2.1

10. RMS Temperature Errors, 0-1500 m, Years 101-200

11. Temperature Anomalies at 1000 m after 190 Years CM2GCM2.1 CM3 CM2M

12. Vertically Integrated Salinity Bias CM2GCM2.1 90 Yrs 190 Yrs

13. Temperature Anomalies at 4000 m after 190 Years CM2GCM2.1 CM2M Climatology

14. PACIFIC AND ATLANTIC OCEANS

15. Pacific Temperature Anomalies after 190 Years CM2GCM2.1 CM3 CM2M

16. Atlantic Temperature Anomalies after 190 Years CM2GCM2.1 CM3 CM2M

17. Atlantic Salinity Anomalies after 190 Years CM2GCM2.1 CM3 CM2M

18. AMOC Strength in 1990 Control Runs 12 Sv 32 Sv Year 600 Year 0

19. Atlantic Salinities and Overturning Streamfunction CM2GCM2.1 CM3 CM2M

20. Denmark Strait Topography in CM2.1 and CM2G CM2G CM2.1/CM2M/CM3 An excessively deep Denmark Strait sill is ubiquitous in IPCC/AR4 models. In CM2G the Denmark Strait and Faroe Bank Channel sill depths in CM2G are set to agree with observed, although the channels are too wide. 9 Sv3.5 Sv

21. AN IDEALIZED GLOBAL WARMING SIMULATION

22. Changes after 110 Years in 1% per year CO 2 Runs CM2.1CM2G Atlantic Temperature Change & Overturning Streamfunction SST Change

23. Summary GFDL will be using 3 new coupled climate models for IPCC AR5 (CM2G, CM2M, and CM3) plus CM2.1 from AR4. CM2.1, CM2M & CM2G have similar time-mean SST biases; Replacing the atmosphere in CM3 improved several of these. CM2.1, CM2M & CM3 have similar interior ocean bias patterns, but with different magnitudes (the largest biases are in CM3). CM2G has clearly superior thermocline structure & watermass properties, and AMOC structure, and very different abyssal biases. –These differences seem to be mostly due to the inherent nature of the isopycnal vertical coordinate, compared with a geopotential coordinate Some interior ocean basin scale temperature biases can be directly related to surface fresh water forcing biases. Do any of these differences matter for climate change projections?

24. EXTRA SLIDES

28. SURFACE PROPERTIES SST, SSS, AND SEA-ICE

29. RMS Errors in Monthly SSTs

30. 100-Year Mean February SST Errors CM2GCM2.1 Reynolds Climatology RMS February SST Errors: CM2G 1.46°C CM2.1 1.84°C CM2M 2.00°C

31. 100-Year Mean February Depth to SST - 1°C CM2GCM2.1 WOA2001 Climatology

32. 100-Year Mean Sea Surface Salinity CM2.1 CM2G

33. 100-Year Mean Sea Ice Concentration March CM2GCM2.1 September

34. The RMS Annual-Mean SST Error With 1990 Forcing, there is committed warming.

35. Long-term Evolution of Annual Mean SST Errors Year 101-200 1.18°C RMS Year 301-400 1.47°C RMS Year 101-200 1.17°C RMS Year 361-380 1.27°C RMS CM2GCM2.1

36. PACIFIC OCEAN

37. Pacific Ocean Temperatures, ~190 Years CM2GCM2.1 Climatology Zonal Mean Pacific Ocean Potential Temperatures Average of Years 181-200

38. Pacific Temperature Bias, ~190 Years CM2GCM2.1 Climatology Possible causes of biases: CM2.1: Excessive diffusion Overly entraining overflows. Weak abyssal flow. CM2G: Insufficient diffusion. Overly wide abyssal cateracts

39. Pacific Salinity Bias, ~190 Years CM2G63LCM2.1 Climatology Zonal Mean Pacific Ocean Salinities Average of Years 181-200

40. Pacific Equatorial Undercurrent in March (Equator)

41. Pacific Equatorial Undercurrent in October (Equator)

42. Pacific Equatorial Undercurrent in March (140°W)

43. Pacific Equatorial Undercurrent in October (140°W)

44. ENSO Statistics for CM2G

45. ENSO Spectra for CM2M and CM2G CM2M NINO3.4 SpectrumCM2G NINO3.4 Spectrum

46. ATLANTIC OCEAN

47. Atlantic Temperature Bias, ~90 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Potential Temperatures Average of Years 81-100 Excludes most marginal seas

48. Atlantic Temperature Bias, ~190 Years CM2GCM2.1 Climatology Possible causes of Atlantic bias: Committed warming from 1990 forcing Circulation errors Excessive vertical diffusion Excessive exchange with Mediterranean Errors in NADW formation Salty bias from runoff + precip. - evap.

49. Atlantic Temperature Bias, ~290 Years CM2GCM2.1 Climatology Possible causes of Atlantic bias: Committed warming from 1990 forcing Circulation errors Excessive vertical diffusion Excessive exchange with Mediterranean Errors in NADW formation Salty bias from runoff + precip. - evap.

50. Atlantic Salinity Anomalies, ~190 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Salinity Average of Years 181-200 Excludes most marginal seas

51. Atlantic Ocean Temperatures, ~190 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Potential Temperatures Average of Years 181-200 Excludes most marginal seas

52. Atlantic Salinities, ~190 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Salinity Average of Years 181-200 Excludes most marginal seas

53. Atlantic Salinity Anomalies, ~90 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Salinity Average of Years 81-100 Excludes most marginal seas

54. Atlantic Salinity Anomalies, ~290 Years CM2GCM2.1 Climatology Zonal Mean Atlantic Ocean Salinity Average of Years 281-300 Excludes most marginal seas

55. Vertically Integrated Salinity Errors CM2GCM2.1 10 Yrs 90 Yrs

56. INDIAN OCEAN

57. Indian Ocean Temperatures, ~190 Years CM2GCM2.1 Climatology Zonal Mean Indian Ocean Potential Temperatures Average of Years 181-200 Excludes most marginal seas

58. Indian Ocean Temperature Bias, ~190 Years CM2GCM2.1 Climatology Zonal Mean Indian Ocean Potential Temperatures Average of Years 181-200 Excludes most marginal seas

59. Indian Ocean Salinities, ~190 Years CM2GCM2.1 Climatology Zonal Mean Indian Ocean Salinity Average of Years 181-200 Excludes most marginal seas

60. OVERFLOWS & EXCHANGES

61. Resolution requirements for avoiding numerical entrainment in descending gravity currents. Z-coordinate: Require that AND to avoid numerical entrainment. (Winton, et al., JPO 1998) Many suggested solutions for Z-coordinate models:  "Plumbing" parameterization of downslope flow: Beckman & Döscher (JPO 1997), Campin & Goose (Tellus 1999).  Adding a separate, resolved, terrain-following boundary layer: Gnanadesikan (~1998), Killworth & Edwards (JPO 1999), Song & Chao (JAOT 2000).  Add a nested high-resolution model in key locations? Sigma-coordinate: Avoiding entrainment requires that But hydrostatic consistency requires Isopycnal-coordinate: Numerical entrainment is not an issue - BUT If resolution is inadequate, no entrainment can occur. Need

62. GLOBAL ANOMALY PATTERNS AT FIXED DEPTHS

63. Year ~190 Temperature Errors at 100 m Depth CM2GCM2.1 Climatology < 0.5 °C white 1 °C Contour interval

64. Year ~190 Temperature Errors at 250 m Depth CM2GCM2.1 Climatology < 0.5 °C white 1 °C Contour interval

65. Year ~190 Temperature Errors at 600 m Depth CM2GCM2.1 Climatology < 0.5 °C white 1 °C Contour interval

66. Year ~190 Temperature Errors at 1000 m Depth CM2GCM2.1 Climatology < 0.2 °C white 0.5 °C Contour interval

67. Year ~190 Temperature Errors at 1500 m Depth CM2GCM2.1 Climatology < 0.2 °C white 0.5 °C Contour interval

68. Year ~190 Temperature Errors at 2000 m Depth CM2GCM2.1 Climatology < 0.2 °C white 0.5 °C Contour interval

69. Year ~190 Temperature Errors at 3000 m Depth CM2GCM2.1 Climatology < 0.1 °C white 0.2 °C Contour interval

70. Year ~190 Temperature Errors at 4000 m Depth CM2GCM2.1 Climatology < 0.1 °C white 0.2 °C Contour interval