Continental Shelf Research 20 (2000) 189}210 Coupling between the thermohaline, chemical and biological "elds during two contrasting upwelling events o! the NW Iberian Peninsula Carmen G. Castro, F.F. Pe H rez*, X.A. A D lvarez-Salgado, F. Fraga Grupo de Oceanoloxia do Instituto de Investigacio & ns Marin J as (CSIC), C/ Eduardo Cabello, 6, 36208 Vigo, Spain Received 2 August 1998; received in revised form 18 March 1999; accepted 22 July 1999 Abstract The hydrographic, chemical and biological conditions observed during spring and summer upwelling events o! the NW Iberian Peninsula are compared. Meteorological data showed that northeasterly winds were of similar magnitude during both cruises, whereas the e!ect of upwelling was more intense during the spring than during the summer since strati"cation was weaker in spring. In the two situations the recurrent upwelling centre o! Cape Finisterre (433N, 93W) divided the study area into two provinces. The two provinces di!er in the occurrence and intensity of winds and in the origin of the upwelled water. Eastern North Atlantic Central Water of subpolar origin (ENACW  ) was recorded north of Cape Finisterre during the two events. South of the Cape, ENACW  was observed during the spring situation, whereas ENACW of subtropical origin (ENACW  ) prevailed during the summer cruise. Despite the di!erent thermohaline and chemical properties of these two varieties of ENACW, similar nutrient levels were found in the two provinces due to strong remineralisation processes on the southern shelf. In addition, slower horizontal circulation at the southern edge of the upwelling centre and the in#uence of four large embayments (the Rm H as Baixas) south of Cape Finisterre, favoured chlorophyll accumulation south of the upwelling centre, which has similarly been observed in other upwelling centres around the world.  2000 Elsevier Science Ltd. All rights reserved. Keywords: Oceanography; Chemical and biological; Nutrients; Coastal upwelling; NW Iberian Peninsula * Corresponding author. Fax: #34-86-292-762. E-mail address: "z@iim.csic.es (F.F. Pe H rez) 0278-4343/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 8 - 4 3 4 3 ( 9 9 ) 0 0 0 7 1 - 0