Change in pCO_2 through Biological Activity in the Marginal Seas of the Western North Pacific: The Efficiency of the Biological Pump Estimated by a Sediment Trap Experiment

摘要

We have carried out sediment trap experiments and observed seasonal variability in organic and inorganic carbon flux in the marginal seas of the western North Pacific (the Okinawa Trough, Ryukyu Trench, Bering Sea, and Sea of Okhotsk). Using empirical equations describing vertical changes in carbon flux and carbon equilibrium equations, the seasonal change or annual change in pCO_2 of sea water in the upper water layer was estimated for each area. Results showed that biological activity (formation of settling particulate carbon) for each area decreased the pCO_2 all year round. There was significant seasonal variability in the decrease in pCO_2 in the Bering sea and the Sea of Okhotsk. Of the four areas, biological activity in the Bering Sea caused the greatest decrease in pCO_2 (ca. 46 ± 13 ppm year~(-1)). We also estimated the annual mean decrease in pCO_2 owing to biological activity in the northwestern North Pacific, northeastern North Pacific, equatorial Pacific, North Atlantic, Arabian sea, and Antarctic oceans using time-series sediment trap experimental data. Our results show that the efficiency of the biological pump in decreasing pCO_2 is higher in the Antarctic ocean and the northwestern North Pacific, including the Bering Sea, than in other areas.