Ocean Acidification

Time series of biogenic sinking particle flux in the western North Pacific subpolar region over two decades (1989 – 2008), revealed that the biogenic CaCO₃ (CC) flux has shown a significant decreasing trend of 2.7 % year^-1 (annual average, – 0.88 ± 0.13 mg m² day^-1 year^-1) along with the decreasing particulate organic carbon (POC) flux of 0.7 % year^-1 while the biogenic opal (OP) flux had no long-term trend.　Comparing these results with the decreasing rate of satellite-derived surface CC with – 0.7 % year^-1, we concluded that three-fourths of the decreasing trend of CC flux was derived from the strengthening of CaCO₃ dissolution through seawater column due to the weakening of water ventilation and the rest was from the decline of CaCO₃-shelled species, indicating the enhancement of the efficiency in oceanic sequestration of atmospheric CO₂ in the sea surface of this region due to the increase of OP/CC ratio.

Watanabe Y. W., Shigemitsu M., Ujiie T. & Minami H., in press. Decadal shift of biogenic sinking particle flux in the western North Pacific subpolar region. Geophysical Research Letters. Article (subscription required).