Export production of particles to the interior of the equatorial Pacific Ocean during the 1992 EqPac experiment Academic Article uri icon

abstract

  • 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 degrees N, 0 degrees, 2 degrees S, 5 degrees S and 12 degrees S at water depths of approximately 1200 m and 2200 m, and 700 m above the bottom. The opening/closing of the traps was synchronized at 17-day periods, for 21 events, covering a total of 357 days. The average annual particle 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) the maximum annual flux at the equator. Sixty-six per cent of settling particles were carbonate; 24% biogenic SiO2 and 5% organic carbon. The onset of tropical instability waves, marking the year’s El Nino/post-El Nino boundary, was associated with a succession of intervals with greater organic carbon and opal at 5 degrees N, 2 degrees S and 5 degrees S that occurred synchronously with a meridional oscillation of instability waves, while net carbon flux during El Nino and post-El Nino periods did not change. Although organic carbon flux increased at 5 degrees 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 the 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/September that year, zonal average of organic carbon flux increased slightly to 0.5% of primary production. Very little carbon reached the interior 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. The pattern of variability of particle flux at the shallow depths was observed also in deeper traps, without temporal offsets, suggesting a settling particle residence time shorter than the 17-day time-series resolution during most of this experiment.

publication date

  • January 1995