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

Ventilation of the Main ThermoclineAnd Global Climate: An Abridged Progress Report

Nicholas Heavens12 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

• Used NOAA/NCDC Extended Reconstructed Sea Surface Temperature data (ERSST)

• ERSST data poor before 1878

• ERSST data poor in Southern Hemisphere

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

Pacific PC1 Power Spectrum

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TNH (?) (5.5 yrs.)

Pacific PC2/EOF2

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Pacific PC2 Power Spectrum

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TNH

PDOLunarNodalCycle (?)

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

But Is There A Connection?

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

Atlantic PC1/EOF1

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Does not correlate with PDO

Atlantic PC1 Power Spectrum

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Three SignificantLong Period ModesAMO ???? ???

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…

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

Looking at PDFs

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 (?)

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

Comparison

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

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)