Ships of opportunity have been used throughout 2003 and 2004 to investigate the carbon system variability in the Bay of Biscay. The temporal pattern of total inorganic (TIC), excluding the variation due to calcium carbonate processes, was strongly modulated by the thermal evolution representing the 55 and 58% of explained variability during 2003 and 2004, respectively. The nitrate, being a proxy of the vertical water mixing and biological uptake, controlled the remaining percent of TIC variation. The noticeable differences between the two annual cycles were the nitrate concentration, 2 and 5.5 µmol·kg-1, and the nitrate: silicate ratio, 1.8 and 2.9, found during the 2003 and 2004 wintertime, respectively. According to chemical characterisation, the more waters yielded during the winter mixing have corresponded probably to Eastern North Atlantic Central water (ENACW) with different origins, subtropical during 2003 and subpolar during 2004; probably due to interannual changes in the atmosphere-ocean interactions

This work was developed and fnded whitin the ECO project (MCyT REN2002-00503/MAR) and from European Commission (EU FP6 CARBOOCEAN Integrated Project, Contract no: 51176-2)

4 pages, 2 figures, 1 table.-- X International Symposium on Oceanography of the Bay of Biscay, April 19-21 2006, Vigo, Spain

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