The distribution of 226Ra in the Atlantic Ocean

Based on results obtained during the GEOSECS program the primary features of the distribution of²²⁶Ra in the Atlantic Ocean can be defined. Outside the Antarctic no significant variation has been found in the²²⁶Ra content of surface waters. Eighty samples yield an average of 7.4 dpm/100 kg (normalized to a salinity of 35.00‰). Deep waters in the central Atlantic have²²⁶Ra contents several dpm/100 kg higher than expected from the mixing of Antarctic Bottom Water (21.3 dpm/100 kg) and basal North Atlantic Deep Water (10.3 dpm/100 kg). These excesses correlate well with deficiencies in O₂ and excesses in SiO₂. The intermediate water²²⁶Ra maximum in the South Atlantic is associated with the inflow of low-oxygen Circumpolar Intermediate Water beneath the Antarctic Intermediate Water.