New profiles of rare earth elements (REE) and Ce oxidation rate measurements in the Sargasso Sea point to a time variable upper ocean redox cycle of cerium. This cycle is complexly linked to biological and light-mediated reactions, input from dust and rain and thermal stratification. In order to understand the biogeochemical processes operating on REE and Ce redox transformation in the upper oceans, a comprehensive time-series study at the BATS GOFS site in the Sargasso Sea will be conducted. This will be complemented with measurements of REE in rainwater, atmospheric particles and upper waters of the N. Atlantic Ocean.
