GEOCHEMISTRY AND PHYSICS OF OCEAN CIRCULATION 



321 



+40- 





+20- 



ui 

 oc 



UJ 

 X 

 Q. 

 {/) 

 O 



-20 



-40 



- RANGE OF 

 AC"* ATM 



1000 BC TO 

 1890 AD 



(TREE RING 

 DATA) 



t^ 



1890 VALUES 



CORRESPONDING RANGE 

 IN AVERAGE OCEAN 

 CIRCULATION RATES 



.7 



L 



1.4 



Fig. 11. 



•8 .9 1.0 I.I 1.2 1.3 



FRACTION PRESENT CIRCULATION RATE 



Dependence of atmospheric C^VC^- ratio on oceanic mixing rate 



several decades. Short-term worldwide fluctuations and random 

 local changes would not show up in tree ring data. 



In summary, the following conclusions are drawn concerning 

 the use of radioactive tracers in studying large scale ocean circu- 

 lation problems. 



1. As in most investigations, one of the main needs is more data 

 and a more complete correlation of the data with available 

 oceanographic information. This will allow more adequate circu- 

 lation models to be set up. 



2. C^^ appears to be the most powerful of these tracers. Its 

 unique advantages are, first, that tree ring data allow the steady 

 state assumptions to be tested and evaluated, and second, that 

 bomb-produced C^"* will provide an independent check on many 

 steady state predictions. Other long-lived isotopes, such as Ra--^ 

 and Si^", also should prove extremely valuable in their own right 



