Hajime KAWAKAMI

Temporal change in POC fluxes in the western North Pacific.

Biological pump strength estimated form ²³⁴Th in the northwestern North Pacific.

What is ²³⁴Th (Thorium-234)?

²³⁴Th is the short-lived radionuclide (half-life, 24.1 days). This radionuclide is produced in the water column as a dissolved species by radioactive decay of the conservative ²³⁸U (half-life, 4.5 billion years) in seawater and is redistributed between the dissolved and particulate phases depending on particule reactivity and the availability of particle surfaces. Therefore, ²³⁴Th serves as a valuable tracer for studying the rates of particule-associated scavenging and the subsequent particle export from the euphotic zone (e.g., Buesseler, 1998).

What is biological pump?

Atmospheric CO₂ dissolves in the surfece ocean. The dissolved CO₂ is assimilated by phytoplankton in the sunlit layer (photosynthesis) and changes to particlate organic carbon (POC). POC sinks from surface to deep ocean. This role exported carbon to the deep ocean is biological pump.

Biological pump strength in the northwestern North Pacific.

The northwestern North Pacific Ocean experiences intense winter cooling and receives large supplies of nutrients though vertical mixing, resulting in high productivety and biological pump strength in spring and summer (e.g., Takahashi et al., 2002). As the results of our study, annual POC flux in this region was estimated to be 31 gC m^-2 y^-1 (Kawakami and Honda, 2007) and is twice and more higher than average value in the world ocean (13 gC m^-2 y^-1, Lutz et al., 2007).

• 14. Shigemitsu, M., Watanabe, Y.W., Yamanaka, Y., Kawakami, H., Honda, M.C.: Relationship between sinking organic matter and minerals in the shallow zone of the western subarctic Pacific. Journal of Oceanography 66, 697-708 (2010).
• 13. Kawakami, H., Honda, M.C., Matsumoto, K., Fujiki, T., Watanabe, S.: East-west distribution of nutrients and dissolved inorganic carbon in the northern North Pacific in autumn. The Open Oceanography Journal 4, 99-106 (2010).
• 12. Kawakami, H., Honda, M.C., Matsumoto, K., Fujiki, T., Watanabe, S.: East-west distribution of POC fluxes estimated from ²³⁴Th in the northern North Pacific in autumn. Journal of Oceanography 66, 71-83 (2010).
• 11. Honda, M.C., Sasaoka, K., Kawakami, H., Matsumoto, K., Watanabe, S., Dickey T.D.: Application of underwater optical data to estimation of primary productivity. Deep-Sea Research I 56, 2281-2292 (2009).
• 10. Kawakami, H.: Scavenging of 210Po and ²³⁴Th by particulate organic carbon in the surface layer of the northwestern North Pacific Ocean. Far East Journal of Ocean Research 2, 67-82 (2009).
• 9. Kawakami, H., Yang Y.-L., Kusakabe, M.: Distributions of 210Po and 210Pb radioactivity in the intermediate layer of the northwestern North Pacific. Journal of Radioanalytical and Nuclear Chemistry 279, 561-566 (2009).
• 8. Fujiki, T., Matsumoto, K., Honda, M.C., Kawakami, H., Watanabe, S.: Phytoplankton composition in the subarctic North Pacific during autumn 2005. Journal of Plankton Research 31, 179-191 (2009).
• 7. Kawakami, H., Kusakabe, M.: Surface water mixing estimated from 228Ra and 226Ra in the northwestern North Pacific. Journal of Environmental Radioactivity 99, 1335-1340 (2008).
• 6. Kawakami, H., Honda, M.C., Wakita., M, Watanabe, S.: Time-series observation of dissolved inorganic carbon and nurtients in the northwestern North Pacific. Journal of Oceanography 63, 967-982 (2007).
• 5. Kawakami, H., Honda, M.C.: Time-series observation of POC fluxes estimated from ²³⁴Th in the northwestern North Pacific. Deep-Sea Research I 54, 1070-1090 (2007).
• 4. Honda, M.C., Kawakami, H., Sasaoka, K., Watanabe, S., Dickey, T.: Quick transport of primary produced organic carbon to the ocean interior. Geophysical Research Letters 33, 10.1029/2006GL026466 (2006).
• 3. Kawakami, H., Yang, Y-L., Honda, M. C., Kusakabe, M.: Particulate organic carbon fluxes estimated from ²³⁴Th deficiency in winters and springs in the northwestern North Pacific. Geochemical Journal 38, 581-592 (2004).
• 2. Murata, A., Kumamoto, Y., Saito, C., Kawakami, H., Asanuma, I., Kusakabe, M., Inoue, H.Y.: Impact of a spring phytoplankton bloom on the CO₂ system in the mixed layer of the northwestern North Pacific. Deep-Sea Research II 49, 5531-5555 (2002).
• 1. Kuma, K., Katsumoto, A., Kawakami, H., Takatori, F., Matsunaga, K.: Spatial variability of Fe(III) hydroxide solubility in the water column of the northern North Pacific. Deep-Sea Research I 45, 91-113 (1998).

• PADI, Advanced Open Water Diver
• Ski Association of Japan, First Degree