The vicinity of the Strait of Gibraltrar: A source of a permanent high productivity

Satellite infrared imagery shows that a cooling of the sea furface occurs in the Strait of Gibraltar and along the Spanish coast in the Alboran Sea. Since this cooling has an internal origin, it implicates also a nutrient transport into the photic zone. A high chlorophyll area off the Spanish coast, also shown by ocean color imagery (CZCS, Nimbus 7) demonstrate a high productivity. Hydrological and chemical observations made during the French MEDIPROD IV cruise on the Jean-Charcot allow to explain this high productivity. The high productivity entertains at mid-depth, by organic sedimentation, an oxygen minimum layer which corresponds to a nutrient maximum (phosphate and nitrate). This high biological activity is useful for hydrological purposes since the tracer qualities of biochemical parameters lead to a better understanding of the circulation pattern and especially of the origin of the Mediterranean outflow.