1. Timing and Climatic Consequences of the Opening of Drake Passage H. D
Timing and Climatic Consequences of the Opening of Drake Passage H.D. Sher E.E. Martin, Nature. 2006

2. Evidence Abrupt climate reversal Increased biological productivity
34Ma: Permanent glaciation of Antarctica
Increased biological productivity

3. Hypotheses Opening of Drake Passage Increased inter-basin exchange
This leads to upwelling induced productivity in the Ocean
Reduced poleward heat transport to Antarctica

4. Method Neodymium isotope ratio Nd143/Nd144
Ratio is high (more radiogenic) on the Pacific sector of Antarctica. Due to the presence of young volcanic rock in this sector. ND=-3
In the Atlantic sector, the terrain is much older and have much lower ND ratio. ND=-9
Ferro-Manganese ocean crust and fossil fish teeth preserves the Nd signal.
Fossil fish teeth have a better resolution than ocean crust

5. Neodymium record 46Ma to present

6. Interpretation
Atlantic sector water mixes with Pacific sector waters (radiogenic). OR
Pacific water enters the Atlantic sector (Indian Ocean)  90 east ridge forms a barrier between east-west of the ridge
Pacific water enters the Atlantic through the Panama passage  Romanche Fracture zone and Walvis ridge show no signs of Pacific water intrusions.

7. Problems Why is the signal at Maud Rise less significant?
Ocean stratified, and the Pacific signal remained at depth
Proto Polar Front at Maude rise which would have isolated the water at Maude rise from the influence from the Pacific sector. This front is apparent in paleo productivity across that front from one side to the other

8. Hypothesis
Opening of Drake Passage  increase mixing in the southern ocean  more nutrient upwelling  more productivity  more carbon sequestration  less CO2 in the atmosphere
And possibly less poleward heat transport associated with the opening of the Drake Passage

9. Delta O18 record 70Ma to present