Tracing the upwelling process in the northern Benguela upwelling system (nBUS) by ¹²⁹I

New data on the presence of ¹²⁹I in seawater in the Southern Hemisphere measured by Accelerator Mass Spectrometry (AMS) is presented. The samples were collected in 2014 along the Namibian coast during a cruise organised by the National Marine Information and Research Centre (NatMIRC), the national laboratories of the Ministry of Fisheries and Marine Resources (MFMR) in Namibia, and the IAEA Environment Laboratories (IAEA NAEL) in Monaco. The Benguela upwelling system is known as one of the most important marine upwelling regions in the world. Strong winds induce an offshore transport of surface seawater which is substituted by cool subsurface water inshore. As this water is nutrient-rich, which leads to high primary productivity, the Benguela upwelling system has a very important role as a fishing production area. The ¹²⁹I concentrations in samples were between (0.66 ± 0.14) × 10⁷ and (1.45 ± 0.30) × 10⁷ atoms/kg. The highest ¹²⁹I concentrations were found in the offshore surface samples. Deep-sea and inshore samples contained lower ¹²⁹I concentrations, possibly as an effect of the upwelling process. A comparison with previously published studies suggests that the presence of ¹²⁹I in the northern Benguela upwelling system (nBUS), is mainly due to the impact of nuclear weapons global fallout, without any evident impact of nuclear fuel reprocessing.