| Summary: | New production (NP) is calculated for NW Iberian shelf waters from 42° to 43°N (3500 km 2 ), 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 C m -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 1998–1999 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.
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