RARE-EARTH ELEMENTS IN THE MEDITERRANEAN-SEA AND MIXING IN THE MEDITERRANEAN OUTFLOW

Mediterranean surface waters contain elevated levels of the rare earth elements compared to similar nutrient-depleted open ocean waters. Application of a flux balance model shows that the Mediterranean is a net sink for Ce and a net source for the other REE. The abundance pattern of the excess REE required for mass balance is enriched in heavy REE and has a negative Ce anomaly. This supports a marine, possibly coastal, source for the REE. Although the magnitudes of the fluxes involved are consistent with aeolian input, an aeolian source would require large-scale removal of Ce and the light REE within the Mediterranean Sea. A mixing model to compute trace metal anomalies in the Mediterranean outflow predicts the observed REE concentrations well. This implies that Ce behaves conservatively in outflow waters over the calculated one-month period for Mediterranean water to reach the study site. Application to other trace metals gives good agreement for Al, Cd and Mn.