A note on the age of radioactive tracers
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 09247963; eISSN 18791573, more
 
Keywords 
Age Isotopes > Radioisotopes Tracers > Radioactive tracers Marine/Coastal 
Author keywords 
age; age of seawater; radioisotope; tracer 
Authors   Top 
 Delhez, E.J.M., more
 Deleersnijder, E., more
 Mouchet, A., more
 Beckers, J.M., more



Abstract 
The age of a water mass is often estimated experimentally using the radioage computed from the distribution of a radioactive tracer (radiocarbon, heliumtritium). Deleersnijder et al. [J. Mar. Syst. 28 (2001) 229.] have shown that the radioage underestimates the age of the water and is larger than the age of the radioactive tracer used for its evaluation. This result is generalized here to radioages computed from the ratio of two radioactive tracers. The differences between the different ages are also studied analytically and numerically as functions of the decay rate of the radioactive tracers. For small decay rates, the difference between the age of the water mass and the radioage is shown to be proportional to the decay rate. It depends also on the level of mixing in the system; even radioactive tracers with small decay rates can provide poor estimates of the age of the water mass in a strongly diffusive flow. For small half lives, both the radioage and the age of radioactive tracers decrease as the inverse of the square root of the decay rate. The same analysis applies to some extent to the estimates of the age of a water mass from stable tracers with known time dependent sources (e.g. chloroflurocarbons). 
