is comparable to the amount transported by the atmosphere. Therefore, it is very important to understand this system. With a half-life of 269 years, argon-39 is particularly well suited to study questions related to ocean circulation. However, its extremely low concentration (argon-39/Ar = 8.1 × 10−16), coupled to its long half-life, makes it impossible to measure the argon-39 decay in any sample of reasonable size.4
AMS using the ATLAS heavy ion accelerator at Argonne National Laboratory has been successful in separating argon-39 from its ubiquitous potassium-39 iso-baric background, the latter being 6-7 orders of magnitude more intense. Measurement of isotopic ratios as small as argon-39/Ar = 4 × 10−17 have been achieved. This program is now poised to measure argon-39 concentrations in ocean water samples in order to explore the oceanic “conveyor belt.”
4 Portions of this paragraph have been adapted from M. Gaelens, M. Loiselet, G. Ryckewaert, et al., 2004, Oceans circulation and electron cyclotron resonance sources: Measurement of the AR-39 isotopic ratio in seawater, Review of Scientific Instruments 75: 1916.