Coupling between the thermohaline, chemical and biological fields during two contrasting upwelling events off the NW Iberian Peninsula

The hydrographic, chemical and biological conditions observed during spring and summer upwelling events off the NW Iberian Peninsula are compared. Met eorological data showed that northeasterly winds were of similar magnitude during both cruises, whereas the effect of upwelling was more intense durin g the spring than during the summer since stratification was weaker in spri ng. In the two situations the recurrent upwelling centre off Cape Finisterr e (43 degrees N, 9 degrees W) divided the study area into two provinces. Th e two provinces differ in the occurrence and intensity of winds and in the origin of the upwelled water. Eastern North Atlantic Central Water of subpo lar origin (ENACW(P)) was recorded north of Cape Finisterre during the two events. South of the Cape, ENACW(P) was observed during the spring situatio n, whereas ENACW of subtropical origin (ENACW(P)) prevailed during the summ er cruise. Despite the different thermohaline and chemical properties of th ese two varieties of ENACW(P) 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 upwe lling centre and the influence of four large embayments (the Rias Baixas) s outh of Cape Finisterre, favoured chlorophyll accumulation south of the upw elling centre, which has similarly been observed in other upwelling centres around the world. (C) 2000 Elsevier Science Ltd. All rights reserved.