DISSOLVED RARE-EARTH ELEMENTS IN THE SOUTHERN-OCEAN - CERIUM OXIDATION AND THE INFLUENCE OF HYDROGRAPHY

Analysis of dissolved REE distributions in the southeastern Atlantic O cean has revealed that progressive oxidative removal of dissolved Ce f rom deepwater (>1 km) occurs over the mixing time of the oceans. Ce-an omaly (Ce/Ce-) values measured in deep-waters from the southeastern A tlantic are similar to, but slightly higher than, those from deep-ocea n stations throughout the Indian and Pacific oceans, typically falling in the range 0.08 less than or equal to Ce/Ce- less than or equal to 0.12. Only deepwater samples from the North Atlantic exhibit values g reater than Ce/Ce- similar to 0.12, with the exception of southeaster n Atlantic bottomwaters which are influenced by Antarctic Bottomwater. Covariation of dissolved REE concentrations with salinity and/or diss olved Si concentrations at this site has allowed dissolved REE composi tions for various Southern Ocean water masses to be predicted. End-mem ber concentrations for Antarctic Bottom Water (AABW) derived in this w ay indicate high dissolved REE concentrations, similar to average Paci fic Deep Water, but with significantly enhanced dissolved Ce concentra tions and less pronounced HREE enrichment. This result is consistent w ith the proximity of our study site to active AABW deepwater formation and evolution of that water mass during transport to the Pacific Ocea n.