Journal of Oceanography

, Volume 61, Issue 6, pp 1075–1087 | Cite as

Seasonal and Interannual Variation of DIC in Surface Mixed Layer in the Oyashio Region: A Climatological View

  • Tsuneo Ono
  • Hiromi Kasai
  • Takashi Midorikawa
  • Yusuke Takatani
  • Kazuhiro Saito
  • Masao Ishii
  • Yutaka W. Watanabe
  • Katsuyuki Sasaki


Eight-year observation results of DIC from 1996 to 2003 in the Oyashio region have been analyzed to obtain a climatological view of its seasonal variation and interannual variation. Data of DIC obtained by several institutes are synthesized to give a dataset with an uncertainty lower than 5 μmol/kg. The obtained climatology of NDIC seasonal variation in the Oyashio mixed layer shows a seasonal amplitude of 176 μmol/kg, with a maximum in January and a minimum in September. These features closely resemble those observed in the southern half of the western subarctic North Pacific (WSNP) including Station KNOT, although the timing of the NDIC maximum is slightly advanced in the case of the Oyashio. Analysis using a quasi-conservative tracer Cp0 (NDIC - 106NP) shows that among 176 μmol/kg of NDIC seasonal variation, only 16 μmol/kg is attributed to hydrographic processes while the remaining 160 μmol/kg is attributed to biological processes. The Cp0 value in the Oyashio mixed layer also resembles that of the WSNP mixed layer during the months May to November, suggesting further resemblance of the Oyashio water mass to that of WSNP in terms of carbon dynamics. The present results also suggest that a single data obtained in Oyashio mixed layer contains 30 μmol/kg of potential uncertainty for the representativity of this region, which leads to a note about a need to treat with caution results obtained by a single observation in this region.


Ocean carbon cycle Oyashio region climatology chemical tracer 


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Copyright information

© The Oceanographic Society of Japan/TERRAPUB/Springer 2005

Authors and Affiliations

  • Tsuneo Ono
    • 1
  • Hiromi Kasai
    • 1
  • Takashi Midorikawa
    • 2
  • Yusuke Takatani
    • 3
  • Kazuhiro Saito
    • 4
  • Masao Ishii
    • 2
  • Yutaka W. Watanabe
    • 5
  • Katsuyuki Sasaki
    • 6
  1. 1.Hokkaido National Fisheries Research InstituteKatsurakoi, KushiroJapan
  2. 2.Meteorological Research InstituteNagamine, TsukubaJapan
  3. 3.Hakodate Marine ObservatoryMihara, HakodateJapan
  4. 4.Kobe Marine ObservatoryWakihama-kaigandori, Chuo-ku, KobeJapan
  5. 5.Graduate School of Environmental Earth ScienceHokkaido UniversityChuo-ku, SapporoJapan
  6. 6.National Research Institute of Fisheries ScienceFukuura, Kanazawa-ku, YokohamaJapan

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