Journal of Oceanography

, Volume 71, Issue 1, pp 19–26 | Cite as

Estimating the nitrate concentration from the dissolved oxygen concentration and seawater temperature in the Kuroshio extension, Oyashio, and mixed water regions

  • Miho IshizuEmail author
  • Chiho Sukigara
  • Toshio Suga
  • Kelvin J. Richards
Original Article


For the purpose of estimating nitrate concentration using the dissolved oxygen concentration and seawater temperature recorded in an instrument such as a profiling float with an oxygen sensor, we examined the relationship between oxygen and nitrate concentrations in the Kuroshio Extension, Oyashio, and mixed water regions (34–43ºN, 140–150ºE) using vertical profile data, which includes temperature, salinity, oxygen, and nitrate, from the World Ocean Database 2005. Examining the NO3/O2 ratio along isotherms, we found a clear linear regression between the oxygen and nitrate concentrations in each potential temperature range, irrespective of water mass and seasonal variation. The slopes represented by the NO3/O2 ratio in each temperature range varied from −0.07 to −0.12. The benefit of analyzing data on constant potential temperature surfaces arises because of the strong dependence of the oxygen saturation of surface waters on temperature. This sets the end point of subducted waters and helps distinguish waters that may have similar preformed nitrate values. Our results suggest that subsequent reminearlization in the subducted water retained the Redfield ratio between N and O2. The estimate of nitrate concentration, by using the oxygen–nitrate relationship discovered in the present study, showed good accuracy with in general a mean error of less than 2.0 μmol/kg. The present method has been demonstrated to be a useful tool for estimating the nitrate concentration from temperature and oxygen.


Oxygen Nitrate Mixed water region between Kuroshio and Oyashio 



The authors thank the members of the Oceanography Group at Tohoku University and at University of Hawaii at Manoa for their helpful discussions throughout this study. Thanks also to Dr. B. Qiu and M. Izumi who carefully read this paper and made suggestions. We would also like to thank anonymous reviewers whose comments have greatly improved the manuscript. This work was supported by “Studies on Prediction and Application of Fish Species Alteration (SUPRFISH)” sponsored by the Agriculture, Forestry and Fisheries Research Council (AFFRC), Japan and the Japanese Agency for Marine Earth Science and Technology. TS was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Grant-in-Aid for Scientific Research on Innovative Areas (22106007).


  1. Anderson LA, Sarmiento JL (1994) Redfield ratios of remineralization determined by nutrient data analysis. Glob Biogeochem Cycles 8(1):65–80CrossRefGoogle Scholar
  2. Boulahdid M, Minster JF (1989) Oxygen consumption and nutrient regeneration ratios along isopycnal horizons in the Pacific Ocean. Mar Chem 26:133–153CrossRefGoogle Scholar
  3. Broecker WS (1974) “NO”, a conservative water-mass tracer. Earth Planet Sci Lett 23(1):100–107CrossRefGoogle Scholar
  4. Broecker WS, Takahashi T, Takahashi T (1985) Sources and flow patterns of deep-ocean waters as deduced from potential temperature, salinity, and initial phosphate concentration. J Geophys Res 90:6925–6939CrossRefGoogle Scholar
  5. Garcia H, Gordon LI (1992) Oxygen solubility in sea water: better fitting equations. Limnol Oceanogr 376:1307–1312CrossRefGoogle Scholar
  6. Ishizu M, Richards K (2013) The relationship between oxygen, nitrate and phosphate in the world ocean based on potential temperature. J Geophys Res Oceans 118:1–9. doi: 10.1002/jgrc.20249 Google Scholar
  7. Jackett DR, McDougall TJ (1997) A neutral density variable for the world’s oceans. J Phys Oceanogr 27(2):237–263CrossRefGoogle Scholar
  8. Kasai H, Saito H, Yoshimori A, Taguchi S (1997) Variability in timing and magnitude of spring bloom in the Oyashio region, the western subarctic Pacific off Hokkaido, Japan. Fish Oceanogr 6:118–129CrossRefGoogle Scholar
  9. Kortzinger A, Hedges JI, Quay PD (2001) Redfield ratios revisited: removing the biasing effect of anthropogenic CO2. Limnol Oceanogr 46(6):964–970CrossRefGoogle Scholar
  10. Limsakul A, Saino T, Goes JI, Midorikawa T (2002) Seasonal variability in the lower trophic level environments of the western subtropical Pacific and Oyashio waters—a retrospective study. Deep-Sea Res Part II 49:5487–5512CrossRefGoogle Scholar
  11. McDougall TJ, Jackett DR (2005) The material derivative of neutral density. J Phys Oceanogr 63:159–185Google Scholar
  12. Noto N, Yasuda I (1999) Population decline of the Japanese sardine with relation to the sea-surface temperature in the Kuroshio Extension. Can J Fish Aqua Sci 56:973–983CrossRefGoogle Scholar
  13. Noto N, Yasuda I (2003) Empirical biomass model for the Japanese sardine with sea surface temperature in the Kuroshio extension. Fish Oceanogr 12:1–9CrossRefGoogle Scholar
  14. Redfield AC, Ketchum BH, Richards FA (1963) The influence of organisms on the composition of sea-water. In: Hill MN (ed) The Sea, vol 2. Interscience, New York, pp 26–77Google Scholar
  15. Riser SC, Johnson KS (2008) Net production of oxygen in the subtropical ocean. Nature 17:323–325CrossRefGoogle Scholar
  16. Saito H, Kasai H, Kashiwai M, Kawasaki Y, Kono T, Taguchi S, Tsuda A (1998) General description of seasonal variations in nutrients, chlorophyll a, and netplankton biomass along the A-line transect, western subarctic Pacific, from 1990 to 1994. Bull Hokkaido Nat Fish Res Inst 62:1–62Google Scholar
  17. Sarmiento JL, Gruber N (2006) Ocean biogeochemical dynamics. Princeton University Press, PrincetonGoogle Scholar
  18. Shimizu Y, Yasuda I, Ito S (2001) Distribution and circulation of the coastal Oyashio intrusion. J Phys Oceanogr 31:1561–1578CrossRefGoogle Scholar
  19. Shiomoto A, Sakai K, Shimoda T, Matsumura S (1994) Primary production in the offshore Oyashio in the spring and summer 1990. J Oceanogr 50:515–529CrossRefGoogle Scholar
  20. Talley LD (1993) Distribution and formation of North Pacific intermediate water. J Phys Oceanogr 23:517–567CrossRefGoogle Scholar
  21. Weiss RF (1970) The solubility of nitrogen, oxygen and argon in water and sweater. Deep-Sea Res 17:721–735Google Scholar
  22. Whitney FA, Freeland HJ, Robert M (2007) Persistently declining oxygen levels in the interior waters of the eastern subarctic Pacific. Prog Oceanogr 75:179–199CrossRefGoogle Scholar
  23. Yasuda I, Kitagawa D (1996) Locations of early fishing grounds of saury in the North-western Pacific. Fish Oceanogr 5:63–69CrossRefGoogle Scholar
  24. Yasuda I, Watanabe Y (1994) On the relationship between the Oyashio front and saury fishing grounds in the north-western Pacific. Fish Oceanogr 3:172–181CrossRefGoogle Scholar
  25. Yasuda I, Okuda K, Shimizu Y (1996) Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone. J Phys Oceanogr 26:448–464CrossRefGoogle Scholar
  26. Yasuda I, Sugisaki H, Watanabe Y, Minobe S, Oozeki Y (1999) Interdecadal variations in Japanese sardine and ocean/climate. Fish Oceanogr 8:18–24CrossRefGoogle Scholar

Copyright information

© The Oceanographic Society of Japan and Springer Japan 2014

Authors and Affiliations

  • Miho Ishizu
    • 1
    Email author
  • Chiho Sukigara
    • 2
  • Toshio Suga
    • 3
  • Kelvin J. Richards
    • 4
  1. 1.Atmosphere and Ocean Research Institute, The University of TokyoKashiwa-shiJapan
  2. 2.Hydrospheric Atmospheric Research CenterNagoya UniversityNagoyaJapan
  3. 3.Department of Geophysics, Graduate School of ScienceTohoku UniversitySendaiJapan
  4. 4.Department of Oceanography, International Pacific Research CenterUniversity of Hawaii at ManoaHonoluluUSA

Personalised recommendations