Summary and Conclusions

1. Although fluxes of total mass, OM, carbonate, biogenic opal, and lithogenics showed definite seasonal change, the annual mean fluxes generally increased from south to north. Diatoms played a significant role in OM and biogenic opal fluxes at the subarctic station (Site 8), while coccolith and foraminifera were important at the subtropical station. In general, an increase in OM flux was associated with higher opal/carbonate and COrganic/CCarbonate ratios in the central North Pacific.

2. Dust particles originating from the Asian continent contributed to lithogenic flux in the central North Pacific. The injection of aerosol-derived iron from Asia has a potential role in enhancing primary and export production in this area, unless other nutrients such as phosphate and nitrate become limiting. The maximum lithogenic flux of the settling particles into the ocean's interior lagged behind the maximum aerosol concentration in the atmospheric column. A plausible explanation for the time lag could be that eolian dust was transported from the source region to the sea through the atmosphere, remained suspended in the upper water column of the Kuroshio Current and/or Kuroshio Extension for some time, and was then removed by incorporation into biogenic pellets or amorphous aggregates when primary production became enhanced.

3. The significantly higher biogenic opal flux measured in the Pacific as compared with the Atlantic can be ascribed to higher concentrations of nutrients in central North Pacific surface waters.

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