1. Paleoceanography

2. The Start ► HMS Challenger 1700s—info about sed distribution ► Piston corer (1940’s) showed CaCO3 ► Ocean environment varied ► Challenged notion of unchanging oceans

3. ► C. Emiliani (1950s) founded science of paleoceanography  Studied SST changes from CaCO3 O2 isotopes

4. ► Sed record extends to 180 my

5. Cenozoic PlExampleate Motions ► Warm water forams decrease at about 4 m.y. ► Diatoms more abundant ► Warm water Pacific/Atl communication ceases ► Pacific is colder ► May initiate glaciation

6. Vostok Ice Core Record

7. Proxies ► Can’t measure ancient oceans ► Use proxies=substitutes in seds, ice  Marine organisms best ► Ecological preferences  Temp, pressure, salinity, etc.

8. Sea Surface Temperatures ► See cycles in sea temperature record ► Related to Milankovitch Cycles  Changes in Earth’s orbit ► Doesn’t explain everything

9. Oxygen Isotope Proxy ► Use calcium carbonate planktonic forams ► Lower T = high O18/O16 ratio  Ratio depends on species  Seawater evaporation, light O16 removed  Precipitation= heavier O18  Both processes deplete oceanic O16

10. Oxygen Isotope Continued ► Must remove ice volume ► Use benthic forams ► Subtract benthic delta 18O from planktonic

11. Other Proxies ► Mg/Ca ratios-planktonic forams  Vary with T  Does not vary with ice volume ► Problem, most carbonate sed below CCD  Poorly preserved forams ► Ocean circulation  Use cadmium proxy  Older waters = more nutrients  Surface water lower cadium concentration  Cadmiu/calcium ratio in foram = cadmium/calcium ratios in seawater  Last 400K cadmium/calcium ratios higher in seds during glacials  More nutrients, less NADW

12. Carbon Isotope Proxy ► Carbon occurs as 12C&C13 ► Photosynthesis favors 12C  Organic matter enriched in 12C, depleted 13C ► Nutrient poor waters=higher 13C/12C like N. Atlantic  Pacific lower ratios ► Glacial times = lower ratios in N. Atlantic = less NADW

13. Gas Hydrates ► Large negative changes in delta 13C at Paleocene/Eocene boundary ► High latitude surface temperates 5-7oC higher  30-40% benthic forams extinct ► Cause, great infusion of 12C— gas hydrates  Methane has negative delta13C  Lead to greenhouse effect ► Quaternary CO2 levels not as high as present ► Need to study sediments to predict future

14. Carbonate System ► Track CCD changes  Sediment below CCD=20% or less carbonate ► Glacial times CCD deeper in Pacific/Indian Oceans  More CO3 in deep water ► Less CO2 in atmosphere ► Or more bacterial respiration  H2O+CO2+CaCO3-Ca2+HCO3- ► Also, increased biological productivity, decreases atmospheric CO2  Opposite in Atlantic