CLIVAR/GODAE Synthesis Evaluation

1. CLIVAR/GODAE Synthesis Evaluation Tony Lee, JPL • Item#5: volume transport, temperature & salinity fluxes through key straits: • Indonesian throughflow (ITF) • ACC at Drake Passage • Florida Current at Florida Strait

2. RTS smoother 3D-VAR Some details about legends

3. ITF

4. ITF volume transport (Sv) Total Spinup problem Island Rule doesn’t work? Or effect of geometry/topography? Anomaly relative to 1993-2001 mean Remarkable consistency

5. ITF volume transport from 1992 (Sv) Total Anomaly relative to 1993-2001 mean

6. ITF temperature flux (PW) Total Anomaly relative to 1993-2001 mean

7. ITF temperature flux from 1992 Total Anomaly relative to 1993-2001 mean

8. ITF salinity flux Total Anomaly relative to 1993-2002 mean

9. ITF salinity flux from 1992 Total Anomaly relative to 1993-2001 mean

10. 1993-2001 averaged seasonal anomaly of ITF

11. ITF property flux (volume, heat, and salt) estimated by various products are overall consistent (for mean as well as for seasonal, interannual, and decadal variability: e.g., large magnitude of seasonal cycle relative to mean value, low ITF during El Nino, lack of decadal variability.

12. ACC

13. ACC volume transport Total Anomaly relative to 1993-2001 mean

14. ACC volume transport from 1992 Total Anomaly relative to 1993-2001 mean

15. ACC temperature flux Total No such large adjustment in volume transport Relatively consistent decadal variability Anomaly relative to 1993-2001 mean

16. ACC temperature flux from 1992 Total Anomaly relative to 1993-2001 mean

17. ACC salinity flux Total Anomaly relative to 1993-2001 mean

18. ACC salinity flux from 1992 Total Anomaly relative to 1993-2001 mean

19. 1993-2001 averaged seasonal anomaly of ACC

20. Relatively large difference in mean and seasonal variability, but relatively consistent on decadal time scale.

21. Florida Current at Florida Strait

22. Two different ways of computing Florida Current (FC) transport by various groups: • meridional transport near 26.5N between Florida (~80W) to 75W (more consistent with cable measurements), • zonal transport between Florida and Cuba (better defined in models). • The time mean of (2) is significantly smaller than that of (1) because a portion of (1) comes through a “short circuit” north of the Caribbean instead of from the loop Current (esp. in models)

23. FC volume transport Total Grey curve – cable data Anomaly relative to 1993-2001 mean

24. FC volume transport from 1992 Total Grey curve – cable data Anomaly relative to 1993-2001 mean

25. Zonal (upper) and meridional (lower) Florida Current transports Zonal: between Florida & Cuba (well-defined) Meridional: 26.5N, 80-75W (near cables) Grey curve – cable data

26. FC temperature flux Total Anomaly relative to 1993-2001 mean

27. FC temperature flux from 1992 Total Anomaly relative to 1993-2001 mean

28. FC salinity flux Total Anomaly relative to 1993-2001 mean

29. FC salinity flux from 1992 Total Anomaly relative to 1993-2001 mean

30. 1993-2001 averaged seasonal anomaly of Florida Current

31. Relatively large spread, partly because of definition problem. In most models, the flow going into the Gulf of Mexico is weak; some flow take a short cut north of Cuba to joint the Florida Current.

32. Summary Statistics

33. 1993-2001 mean transports/fluxes: For Florida Current: black - meridional transport near 26.5N, 80-75W; red – zonal transport between Florida & Cuba.

34. The largest mean ITF (> 23Sv): consistent with Island rule (integration of South Pacific curl)? Or effect of geometry/topography? High mean ACC transports (170-180 Sv): too strong zonal wind? lack of form drag due to smooth topography? Small viscosity?

35. 1993-2001 rms variability of volume transport, rms difference among models, and rms difference from cable measurements