Nutrient distributions during an annual cycle across a warmcore eddy from the E. Mediterranean Sea

A detailed description of the physical, chemical and biological structure of the Cyprus eddy is given from cruises carried out in February, May, September and November 1989. The chemical data support the suggestion (Brenner et al., Dynamics of Atmospheres and Oceans, 15, 457-477, 1991) that this eddy forms essentially in situ by the injection of 250-300 m of Levantine Intermediate Water into the upper layers of the water column. The nitrate vs temperature profile is characteristic of this longitude and not of one transported rapidly from farther west. The silicate vs depth profile at the boundary can be superimposed on that from the core if its is displaced downward by 250 m. The depth of the nitrate maximum in the core also is displaced downward by 250-300 m relative to the boundary. There was no evidence of a different origin of the core water based on nutrient profiles on Sigma-T surfaces. These data suggest that the Cyprus eddy is similar in many respects to a mid-ocean eddy, not a ring. There was enhanced productivity in the core of the eddy in winter. This bloom occurred simultaneously with deep (> 350 m) mixing of the water column, and possibly in part as the result of algal growth at unusually low light levels. There was no evidence of enhanced productivity at the boundary of the eddy, suggesting that the upwelling of nutrients was weak and that the enhanced productivity observed in the boundary of rings is more related to the strong temperature front or entrainment of shelf waters. It is cautioned that several important physical and biological features of this eddy would not have been seen using satellite imagery.