Decadal shift of biogenic sinking particle flux in the western North Pacific subpolar region

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, -0.880.13mgm(2)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. Key Points CaCO3 and organic carbon sinking fluxes had decreasing trends