TERRAPUB Journal of Oceanography

Journal of Oceanography, Vol. 64 (No. 6), pp. 911-923, 2008

Deep Sea Circulation of Particulate Organic Carbon in the Japan Sea

Shigeyoshi Otosaka1,2*, Takayuki Tanaka1,2, Orihiko Togawa1, Hikaru Amano1,2, Eugeny V. Karasev3, Masayuki Minakawa4 and Shinichiro Noriki5

1Research Group for Environmental Science, Japan Atomic Energy Agency, Shirakata-Shirane, Tokai, Ibaraki 319-1195, Japan
2AMS Management Section, Japan Atomic Energy Agency, Mutsu, Aomori 035-0064, Japan
3Far Eastern Hydrometeorological Research Institute, Fontanaya St., Vladivostok 690600, Russia
4Marine Productivity Division, National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama 236-8648, Japan
5Laboratory of Marine and Atmospheric Geochemistry, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan

(Received 20 September 2007; in revised form 30 May 2008; accepted 30 May 2008)

Abstract: 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 (14C) measurements were also carried out. Annual mean POC flux at 1 km depth was 30.7 mg m-2day-1 in the western Japan Basin, 12.0 mg m-2day-1 in the eastern Japan Basin and 23.8 mg m-2day-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 Δ14C values (>0‰) and aged POC (Δ14C < -40‰) was observed in winter (December-January). The Δ14C values in sinking POC were negatively correlated with aluminum concentration, indicating that Δ14C is strongly related to the lateral supply of lithogenic materials. The Δ14C values also showed correlations with excess manganese (Mnxs) concentrations in sinking particles. The Δ14C-Mnxs 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 Δ14C-Mnxs relationships between the Japan Basin and the Yamato Basin, we consider that basin-scale transport processes of POC occur in the Japan Sea.

*Corresponding author E-mail: otosaka.shigeyoshi@jaea.go.jp

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