EXPORT PRODUCTION OF PARTICLES TO THE INTERIOR OF THE EQUATORIAL PACIFIC-OCEAN DURING THE 1992 EQPAC EXPERIMENT

Twenty-four time-series, moored sediment traps were deployed between 2 /2/92 and 1/27/93 along 140 degrees W at 9 degrees N, 5 degrees N, 2 d egrees N, 0 degrees, 2 degrees S, 5 degrees S and 12 degrees S at wate r depths of approximately 1200 m and 2200 m, and 700 m above the botto m. The opening/closing of the traps was synchronized at 17-day periods , for 21 events, covering a total of 357 days. The average annual part icle flux in the ocean's interior (2.2 to 4.4 km deep) from 5 degrees N to 5 degrees S was 28.5 g m(-2) year(-1),with 34.8 g(-2) year(-1) th e maximum annual flux at the equator. Sixty-six per cent of settling p articles were carbonate; 24% biogenic SiO2 and 5% organic carbon. The onset of tropical instability waves, marking the year's El Nino/post-E l Nino boundary, was associated with a succession of intervals with gr eater organic carbon and opal at 5 degrees N, 2 degrees S and 5 degree s S that occurred synchronously with a meridional oscillation of insta bility waves, while net carbon flux during El Nino and post-El Nino pe riods did not change. Although organic carbon flux increased at 5 degr ees N, 2 degrees S and 5 degrees S during the post-El Nino period, it was counterbalanced by decreases at the upwelling stations (2 degrees N and the equator), resulting in no net carbon flux increase across th e 5 degrees N to 5 degrees S region. In February/March 1992, only 0.34 % of the organic carbon fixed by primary production over the 5 degrees N to 5 degrees S zone arrived in the ocean's interior. In August/Sept ember that year, zonal average of organic carbon flux increased slight ly to 0.5% of primary production. Very little carbon reached the inter ior depths of the upwelling stations; however, the fraction of export was higher at the 5 degrees N, 2 degrees S and 5 degrees S stations. T he pattern of variability of particle flux at the shallow depths was o bserved also in deeper traps, without temporal offsets, suggesting a s ettling particle residence time shorter than the 17-day time-series re solution during most of this experiment.