New production of the NW Iberian shelf during the upwelling season over the period 1982-1999

New production (NP) is calculated for NW Iberian shelf waters from 42degrees to 43degreesN (3500 kM2), at the fortnight, upwelling-season (March-October) and inter-annual time-scales. The time series used are (1) upwelling rates (daily values of offshore Ekman transport from 1982 to 1999), (2) bottom shelf temperatures (twice a week values from 1987 to 1999), and (3) the nutrient-temperature relationships of upwelled Eastern North Atlantic Central Water (ENACW) obtained during 14 hydrographic cruises to the study area (between 1977 and 1998). Marked inter-annual variability is observed, both at the fortnight and the seasonal time-scales. Average NP over the upwelling-season ranged from 330 to 815 mg C m(-2) d(-1) (mean, 490+/-145 mg Cm-2 d(-1)) in the 1982-1999 period. Large inter-annual changes of upwelling rates are the reason behind the NP fluctuations: 83% of the variability of NP can be explained by the offshore Ekman Transport (-Q(X)). NP is compared with satellite-derived net microbial community production (NCP) during the 19981999 upwelling seasons, when SeaWiFS images are available. An average upwelling-season NP/NCP ratio of 0.33 was obtained, indicating that 67% of NCP is respired in situ and 33% is exported off-shelf to the surrounding oligotrophic ocean. (C) 2002 Elsevier Science Ltd. All rights reserved.