New production of the NW Iberian shelf during the upwelling season over the period 1982e1999

• Main Authors: X A ! Alvarez-Salgado, S Beloso, I Joint, E Nogueira, L Chou, F F P! Erez, S Groom, J M Cabanas, A P Rees, M Elskens
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1081.45; http://www.vliz.be/imisdocs/publications/32841.pdf

Abstract New production (NP) is calculated for NW Iberian shelf waters from 421 to 431N (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 À2 d À1 (mean, 4907145 mg C m À2 d À1 ) 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 ðÀQ X Þ: 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. r