TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 65 (No. 3), pp. 397-406, 2009

Radionuclides as Tracers of Water Fronts in the South Indian Ocean—ANTARES IV Results

Sang-Han Lee1, Pavel P. Povinec2*, Janine Gastaud3, Beniamino Oregioni3, Laurent Coppola4 and Catherine Jeandel4

1Korea Research Institute of Standards and Science, Daejeon 305-600, Republic of Korea
2Comenius University, Faculty of Mathematics, Physics and Informatics, SK-84248 Bratislava, Slovakia
3International Atomic Energy Agency, Marine Environment Laboratories, MC-98000, Monaco
4CNRS/CNES/IRD/Université de Toulouse, Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, F-31400 Toulouse, France

(Received 19 June 2008; in revised form 6 February 2009; accepted 6 February 2009)

Abstract: Anthropogenic 90Sr, 239,240Pu and 241Am were used as tracers of water mass circulation in the Crozet Basin of the South Indian Ocean, represented by three main water fronts—Agulhas (AF), Subtropical (STF) and Subantarctic (SAF). Higher 90Sr concentrations observed north of 43°S were due to the influence of AF and STF, which are associated with the south branch of the Subtropical gyre, which acts as a reservoir of radionuclides transported from the North to the South Indian Ocean. On the other hand, the region south of 43°S has been influenced by SAF, bringing to the Crozet Basin Antarctic waters with lower radionuclide concentrations. The 238Pu/239,240Pu activity ratios observed in water and zooplankton samples indicated that, even 35 years after the injection of 238Pu to the Indian Ocean from the burn-up of the SNAP-9A satellite, the increased levels of 238Pu in surface water and zooplankton are still well visible. The radionuclide concentrations in seawater and their availability to zooplankton are responsible for the observed 210Po, 239,240Pu and 241Am levels in zooplankton.

*Corresponding author E-mail: povinec@fmph.uniba.sk

[Full text] (PDF 335 KB)