alley’s ‘wally was right: predictive ability of the north atlantic “conveyor belt”...
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Alley’s ‘Wally Was Right: Predictive Ability of the North
Atlantic “Conveyor Belt” Hypothesis for Abrupt Climate
Change’Jake Leech
29 Aug 08
Bestiary
Wally’s Arguments
• Greenland proxies all show abrupt climate change
• Greenland data matches Europe data
• Data matches expectations from North Atlantic SST changes
• MOC switching is possible
• Data shows ocean circulation changes
Ice core data
Hemispheric See-Saw
Modelled climate patterns seem to match Voelker data set
See Saw in Data
Response of MOC to freshwater
Sea Ice and Seasonality
Wally’s data
• Young, surface waters are depleted in Cd and C-12, and enriched in C-14
• SH water is “older”
• During cold periods, NH sediments are “older”
Jean’s Data
• Benthic forams have heavier oxygen isotopes in colder water and saltier water, and therefore in denser water.
• Density profiles can be used to reconstruct geostrophic flow through the Florida Straits, which shows changes in MOC.
Jerry’s Data
• Water is stripped of Pa and Th before entering the North Atlantic
• Thorium is stripped out of the water within 20-40 years, before being exported
• Protactinium is stripped out of the water within 100-200 years, after being exported.
Jerry’s Data vs. Forams
Caveats
• Background state is important.
• Freshwater forcing? Cooling events and freshwater pulses are correlated, but which causes which?
• 1500 year oscillation?
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