Ventilation of the Main Thermocline And Global Climate: An Abridged Progress Report
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Ventilation of the Main ThermoclineAnd Global Climate: An Abridged Progress Report
Nicholas Heavens12 February 2006
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Summary
• 1. Data Analysis of Patterns of Long Period SST Variability
• 2. Comparison with Results of GCMs
• 3. Searching for Norden Huang’s c5
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Data Analysis Considerations
• Used NOAA/NCDC Extended Reconstructed Sea Surface Temperature data (ERSST)
• ERSST data poor before 1878
• ERSST data poor in Southern Hemisphere
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Poor Data Before 1878
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Poor Data in the SH
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Pacific PC1/EOF1
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Correlation is r=0.69 with PDO Index, 0.78 with weighted PC2
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Pacific PC1 Power Spectrum
QuickTime™ and aTIFF (LZW) decompressor
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TNH (?) (5.5 yrs.)
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Pacific PC2/EOF2
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Pacific PC2 Power Spectrum
QuickTime™ and aTIFF (LZW) decompressor
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TNH
PDOLunarNodalCycle (?)
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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
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But Is There A Connection?
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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
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Atlantic PC1/EOF1
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Does not correlate with PDO
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Atlantic PC1 Power Spectrum
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Three SignificantLong Period ModesAMO ???? ???
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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…
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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
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Looking at PDFs
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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 (?)
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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
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Comparison
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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
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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)