Transport of North Pacific 137Cs labeled waters to the south-eastern Atlantic Ocean

Abstract During the reoccupation of the WOCE transect A10 at 30°S by the BEAGLE2003 cruise, the SHOTS project partners collected a large number of samples for the analysis of isotopic tracers. 137 Cs was mostly deposited on the oceans surface during the late 1950s and early 1960s, after the atmospheric detonation of large nuclear devices, which mostly occurred in the Northern Hemisphere. The development of advanced radioanalytical and counting techniques allowed to obtain, for the first time in this region, a zonal section of 137 Cs water concentrations, where little information existed before, thus constituting an important benchmark for further studies. 137 Cs concentrations in the upper waters (0–1000 m) of the south-eastern Atlantic Ocean are similar to those observed in the south-western Indian Ocean, suggesting transport of 137 Cs labeled waters by the Agulhas current to the Benguela Current region. In contrast, bomb radiocarbon data do not show this feature, indicating the usefulness of 137 Cs as a radiotracer of water mass transport from the Indian to the South Atlantic Ocean.