Pergamon 0079-6611(94) 00005-0 Prog. Oceanog. Vol. 33, pp. 249-302, 1994 Copyright © 1994 Elsevier Science Ltd Printedin GreatBritain.All rightsreserved 0079 - 6611/94 $26.00 Boundary current instabilities, upwelling, shelf mixing and eutrophication processes in the Black Sea HALiLi. StYe., EMIN0ZSOY AND OMiTUNLI3"ATA Institute of Marine Sciences, Middle East Technical University, PK28 Erdemli, "feel, Turkey Abstract - Satellite and in situ data are utilized to investigate the mesoscale dynamics of the Black Sea boundary current system with special emphasis on aspects of transport and productivity. The satellite data are especially helpful in capturing rapid sub-mesoscale motions insufficiently resolved by the in situ measurements. Various forms of isolated features, including dipole eddies and river plumes, are identified in the satellite images. Unstable flow structures at these sites appear to transport materials and momentum across the continental shelf. Species differentiation and competition are evident along the boundary current system and at the frontal regions during the development of early summer productivity. A time series of Coastal Zone Colour Scanner (CZCS) images indicate dynamical modulation of the springtime surface productivity in the southern Black Sea. Unstable meandering motions generated at Sakarya Canyon propag, lte east with speeds of ~ 10-15km dL Within weeks, a turbulent jet is created which separates from the coast, covering the entire southwestern sector. The nutrients driving the phytoplankton production (mainly Emiliana huxleyi) of the current system evidently originate from fluvial discharge entering from the northwestern region including the Danube river. The productivity pattern develops in early summer when the Danube inflow is at its peak, and through meandering motions spreads into an area several times wider than the continental shelf. In 1980, the CZCS data, and in 1991 and 1992, the Advanced Very High Resolution Radiometer (AVHRR) data in.dicate patches of upwelling along the west Anatolian coastline between Sakarya Canyon and Cape Ince (Ince Burun) in summer. The upwelling phenomenon is outstanding because it occurs on a coast where normally the surface convergence near the coast implies downwelling, and under conditions of unfavourable winds. In i 992, the hydrographic data indicated the upwelling to be the result of a surface divergence of the boundary current, and sequences of satellite data indicate the role of transient dynamics. The in situ data showed the upwelling centres to be devoid ofphytoplankton as well as fish eggs and larvae. The AVHRR and in situ hydrographic data in winter 1990 indicate cold water is formed over the entire western Black Sea continental shelf. The band of cold water de crease s in width as it moves south and impinges on the headland at Baba Burnu, where it undergoes a sudden expansion. The maximum winter phytoplankton bloom sampled during the same period indicates explosive populations of diatoms following the band of cold water. 249