Timing and Climatic Consequences of the Opening of

Drake PassageH.D. Sher E.E. Martin, Nature. 2006

Evidence

• Abrupt climate reversal– 34Ma: Permanent glaciation of Antarctica

• Increased biological productivity

Hypotheses

• Opening of Drake Passage• Increased inter-basin exchange• This leads to upwelling induced

productivity in the Ocean• Reduced poleward heat transport to

Antarctica

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

Neodymium record 46Ma to present

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.

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

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

Delta O18 record 70Ma to present