Temperature, salinity, oxygen, nutrients and CO2 data obtained in the areas west and north of the Iberian Peninsula have been analyzed. We assume that the composite parameters such as Broecker's “NO” and “PO” and our own “CAO” and “SiO” are conservative for our water mass analysis. We demonstrate that the observations can be well represented by mixing between five end-members and estimate the relative proportions of these end-members in waters between 40N and 47N. Furthermore, based upon the differences between the observed and computed concentrations of oxygen and nutrients, the approximate rates of oxygen utilization and nutrient production in each water mass are estimated. The type-values of the “NO,” “PO” and “CO” parameters are used to compare the data obtained here with those recorded in other areas.