The Western North Pacific Playing a Key Role in Global Biogeochemical Fluxes

Abstract

The oceanic biogeochemical fluxes in the North Pacific, especially its northwestern part, are discussed to prove their importance on a global scale. First, the air-sea exchange processes of chemical substances are considered quantitatively. The topics discussed are sea salt particles transported to land, sporadic transport of soil dust to the ocean and its role in the marine ecosystem, the larger gas transfer velocity of CO2 indicating the effect of bubbles, and DMS and greenhouse gases other than CO2. Next, chemical tracers are utilized to reveal the water circulation systems in the region, which are the Pacific Deep Water including its vertical eddy diffusivity, the North Pacific Intermediate Water and the Japan Sea Deep Water. Thirdly, the particulate transport process of chemical substances through the water column is clarified by analyzing the distribution of insoluble radionuclides and the results obtained from sediment trap experiments. Fourthly, the northern North Pacific is characterized by stating the site decomposing organic matter and Si playing a key role in the marine ecosystem. Both are induced by the upwelled Pacific Deep Water. Fifthly, the oceanic CO2 system related to global warming is presented by clarifying the distribution of anthropogenic CO2 in the western North Pacific, and roles of the upwelled Pacific Deep Water and the continental shelf zone in the absorption of atmospheric CO2. Finally, Mn and other chemical substances in sediments are discussed as recorders of the early diagenesis and indicators of low biological productivity during glacial ages in the northwestern North Pacific. It is concluded that the western North Pacific is characterized mainly by the Pacific Deep Water bringing nutrients to the northern North Pacific, located at the exit of the global deep water circulation and, therefore, the region plays a key role in the global biogeochemical fluxes.