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Ventilation of the Main Thermocline And Global Climate: An Abridged Progress Report

Ventilation of the Main Thermocline And Global Climate: An Abridged Progress Report Nicholas Heavens 12 February 2006. Summary. 1. Data Analysis of Patterns of Long Period SST Variability 2. Comparison with Results of GCMs 3. Searching for Norden Huang’s c5. Data Analysis Considerations.

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Ventilation of the Main Thermocline And Global Climate: An Abridged Progress Report

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  1. Ventilation of the Main Thermocline And Global Climate: An Abridged Progress Report Nicholas Heavens 12 February 2006

  2. Summary • 1. Data Analysis of Patterns of Long Period SST Variability • 2. Comparison with Results of GCMs • 3. Searching for Norden Huang’s c5

  3. Data Analysis Considerations • Used NOAA/NCDC Extended Reconstructed Sea Surface Temperature data (ERSST) • ERSST data poor before 1878 • ERSST data poor in Southern Hemisphere

  4. Poor Data Before 1878

  5. Poor Data in the SH

  6. Pacific PC1/EOF1 Correlation is r=0.69 with PDO Index, 0.78 with weighted PC2

  7. Pacific PC1 Power Spectrum TNH (?) (5.5 yrs.) PIDO (64 yrs.)

  8. Pacific PC2/EOF2

  9. Pacific PC2 Power Spectrum TNH PDO Lunar Nodal Cycle (?) PIDO

  10. Lunar Nodal Cycle • Precession of Lunar Orbit About Earth (Shift in Lunar Calendars…) • 1 Lunar Epoch=~18.6 yrs, • Causes Variation in Intensity of the Tides • Sea of Okhotsk is important zone of tidal dissipation, tidal mixing may control extrusion of DSW from Northwest Polynya

  11. But Is There A Connection?

  12. Other Components In N. Pacific • Boring (have very weak long period modes, mostly in PIDO territory) • PC4 seems not to be West Pacific Mode (as I first suspected) • PC1 and PC2 explain 44% of variability

  13. Atlantic PC1/EOF1 Does not correlate with PDO

  14. Atlantic PC1 Power Spectrum Three Significant Long Period Modes AMO ???? ???

  15. Other Atlantic PCs • PC2 has Lunar Nodal Mode (Tidal Mixing in the Fram Strait[between Greenland and Spitsbergen) (?) and NAOish mode that I can’t correlate with NAO • Decadal Mode in PC1 recurs in PC2 • PC3 like PC1 but with little decadal mode • PC4 may have TNH and possibly TNH-Decadal Beat…

  16. 2. GCMs and Long Period SST Variability • Two models with suitable output quality • 1. AOGCM from COLA (B. Kirtman et al.) • 2. Hadley Center FAR 2XCO2 run

  17. Looking at PDFs

  18. Problems with GCMs • Seem to have trends associated with systematic bias • Do not produce robust long period modes, contain some interannual variability of interest, greater success in Atlantic may be related to greater open-ocean convection • Full heat budget typically limited to upper 300 m., bad resolution for thermocline ventilation (?)

  19. 3. In Search of Norden Huang’s C5 • Looked at direct forcing of global temperature by SST forcing in analyzed boxes, rough estimate, did not do full analysis of EOF • Used PC1s only

  20. Comparison

  21. Why Doesn’t It Work? • Need More PCs? • Incorrect Hypothesis • EMD Might Not Produced Physically Meaningful Results • Southern Hemisphere Role Significant • Global T Response Function is Non-Linear in the SST Forcing Function

  22. Future Work • Simulation of Vertical Mixing in the North Pacific due to Intense Transients (More fun figures, I promise) • Investigate relations between climatically suspicious current flow and properties and air-sea gas exchange (CH4 in the helf ssediments or N2O in high production zones)

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