Seawater-Particle Interactions of Rare Earth Elements and Neodymium Isotopes in the Deep Central Arctic Ocean

In the central Arctic Ocean, dissolved rare earth element concentrations ([dREE]) and the neodymium (Nd) isotope compositions are constant throughout the deep water column (>1,000 m water depth), indicating unique conditions among the ocean basins and therefore requiring an investigation of seawater-particle interactions. Here, we present the first high-resolution particulate REE and Nd isotope data from the Arctic Ocean and discuss the possible seawater-particle processes affecting the Arctic Ocean. Our results show that particulate [REE] are on the same order of magnitude as in other ocean basins, suggesting that particle composition is the main cause for a lack of pREE release to the dissolved pool. The lithogenic fraction dominates throughout the water column while the biogenic material contribution is very small. This paucity of biogenic material results in reduced particle-seawater exchanges of REEs and Nd isotopes. Moreover, we note only slight differences in the dissolved Nd isotope composition between the Eurasian and Canadian Basins. This is due to the different source regions supplying different dissolved and particulate Nd isotope signatures to both basins. The dissolved [REE] and Nd isotope composition of Atlantic waters are modified during their flow paths through contributions from the Kara Sea, lowering the salinity and increasing [dREE] and dNd isotope compositions. Hydrothermal influence from the Gakkel Ridge on dissolved and particulate [REE] and Nd isotopes could not be detected.