Journal of Oceanography

, Volume 75, Issue 2, pp 195–203 | Cite as

Enhanced vertical turbulent nitrate flux in the Kuroshio across the Izu Ridge

  • T. TanakaEmail author
  • D. Hasegawa
  • I. Yasuda
  • H. Tsuji
  • S. Fujio
  • Y. Goto
  • J. Nishioka
Short Contribution


The first direct measurements of vertical turbulent nitrate flux, FluxNO3, were conducted in the Kuroshio across the Izu Ridge and revealed large FluxNO3 near the sill crest at the 1% light depth. This large FluxNO3 possibly enhances downstream phytoplankton growth. Extremely large FluxNO3 was also observed at 26.0–26.6 σθ between the core of the Kuroshio nutrient stream and the North Pacific Intermediate Water. We hypothesize that strong vertical mixing in the Izu Ridge draws sufficient nitrate upward from the North Pacific Intermediate Water to the nutrient stream, which eventually impacts the downstream biogeochemistry in the western North Pacific.


Vertical turbulent nitrate flux Vertical mixing Izu Ridge Kuroshio Nutrient stream Simultaneous turbulence and nitrate measurement 



We thank the officers, crews, onboard scientists, technical staffs, and graduate students of the R/V Shinsei-maru KS-16-10 cruise. We also thank A. Murayama for her support in the nutrient analysis. Finally, we thank two anonymous reviewers for their valuable comments on the manuscript. This study was supported by Grants-in-Aid for Scientific Research on Innovative Areas (MEXT KAKENHI JP15H05818 and JP15H05820).


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Copyright information

© The Oceanographic Society of Japan and Springer Japan KK, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education AgencyShiogamaJapan
  2. 2.Atmosphere and Ocean Research InstituteThe University of TokyoKashiwaJapan
  3. 3.Hakodate Local Meteorological Office, Japan Meteorological AgencyHakodateJapan
  4. 4.Institute of Low Temperature SciencesHokkaido UniversitySapporoJapan

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