Deep Sea Circulation of Particulate Organic Carbon in the Japan Sea

Seasonal and spatial variations of particulate organic carbon (POC) flux were observed with sediment traps at three sites in the Japan Sea (western and eastern Japan Basin and Yamato Basin). In order to investigate the transport processes of POC, radiocarbon (C-14) measurements were also carried out. Annual mean POC flux at 1 km depth was 30.7 mg m(-2) day(-1) in the western Japan Basin, 12.0 Mg m(-2)day(-1) in the eastern Japan Basin and 23.8 mg m(-2)day(-1) in the Yamato Basin. At all stations, notably higher POC flux was observed in spring (March-May), indicating biological production and rapid sinking of POC in this season. Sinking POC in the high flux season showed modern Delta C-14 values (>0 parts per thousand) and aged POC (Delta C-14 < -40 parts per thousand) was observed in winter (December-January). The Delta C-14 values in sinking POC were negatively correlated with aluminum concentration, indicating that Delta C-14 is strongly related to the lateral supply of lithogenic materials. The Delta C-14 values also showed correlations with excess manganese (Mn-xs) concentrations in sinking particles. The Delta C-14-Mn-xs relationship suggested that (1) the majority of the aged POC was advected by bottom currents and incorporated into sinking particles, and (2) some of the aged POC might be supplied from the sea surface at the trap site as part of terrestrial POC. From the difference in the Delta C-14-Mn-xs relationships between the Japan Basin and the Yamato Basin, we consider that basin-scale transport processes of POC occur in the Japan Sea.