302 



THE DEEP SEA 



If a more complex case were used in which the rate of mixing 

 within the pool is altered with time, steady state would not be 

 achieved and the color pattern would change with time. Interpre- 

 tation of mixing rates from a single color photograph of the 

 system with no knowledge of the manner in which these rates 

 were varying could obviously lead to false conclusions. 



The analogy points out that an understanding of mixing patterns 

 in the ocean is a prerequisite of successful application of radio- 

 isotopes to oceanic mixing. Thus isotope data are useful only when 

 combined with the proper oceanographic information. The 

 analogy also indicates that a single survey of the concentration of 

 a radioactive isotope in the oceans cannot be correctly interpreted 

 without a knowledge of whether or not deep circulation is essen- 

 tially a steady state process. 



Table I lists the most promising radioisotopes along with their 

 half lives and sources. Of these C^^ is probably the most useful 

 because of the rather simple geochemistry of carbon in the oceans 

 and because the dissolved bicarbonate in the oceans is communi- 

 cating with the COo in the atmosphere. The importance of the 

 latter will become clear as the discussion proceeds. H^ Sr^", and 

 Cs'''^ are difficult to use because of their extremely low concen- 

 trations, making measurements tedious and expensive, and because 

 of the complex mode of injection into the system. Recently 

 discovered in oceanic sponges by workers at Scripps, Si'^- promises 

 to be extremely useful in ocean mixing problems. Koczy has 

 shown that Ra--^ is being released into the ocean from the sedi- 

 ments. Much of the potential value of the Ra--'' method lies in 



Table I. Radioisotopes Applicable to Oceanic Mixing Problem 



