caa a22 4500 60545521X CHVBK 20210128100211.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s10872-014-0257-1 doi (NATIONALLICENCE)springer-10.1007/s10872-014-0257-1 Estimating the nitrate concentration from the dissolved oxygen concentration and seawater temperature in the Kuroshio extension, Oyashio, and mixed water regions [Elektronische Daten] [Miho Ishizu, Chiho Sukigara, Toshio Suga, Kelvin Richards] 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 2.0μmol/kg. The present method has been demonstrated to be a useful tool for estimating the nitrate concentration from temperature and oxygen. The Oceanographic Society of Japan and Springer Japan, 2014 Oxygen nationallicence Nitrate nationallicence Mixed water region between Kuroshio and Oyashio nationallicence Ishizu Miho Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8564, Kashiwa-shi, Chiba, Japan aut Sukigara Chiho Hydrospheric Atmospheric Research Center, Nagoya University, F3-1 (200) Furo-cho, Chikusa-ku, 464-8601, Nagoya, Japan aut Suga Toshio Department of Geophysics, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, 980-8578, Sendai, Miyagi, Japan aut Richards Kelvin Department of Oceanography, International Pacific Research Center, University of Hawaii at Manoa, 1680 East-West Road, 96822, Honolulu, HI, USA aut Journal of Oceanography Springer Japan 71/1(2015-02-01), 19-26 0916-8370 71:1<19 2015 71 10872 https://doi.org/10.1007/s10872-014-0257-1 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10872-014-0257-1 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ishizu Miho Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5, Kashiwanoha, 277-8564, Kashiwa-shi, Chiba, Japan aut NATIONALLICENCE 700 1- Sukigara Chiho Hydrospheric Atmospheric Research Center, Nagoya University, F3-1 (200) Furo-cho, Chikusa-ku, 464-8601, Nagoya, Japan aut NATIONALLICENCE 700 1- Suga Toshio Department of Geophysics, Graduate School of Science, Tohoku University, 6-3 Aramaki-aza-Aoba, Aoba-ku, 980-8578, Sendai, Miyagi, Japan aut NATIONALLICENCE 700 1- Richards Kelvin Department of Oceanography, International Pacific Research Center, University of Hawaii at Manoa, 1680 East-West Road, 96822, Honolulu, HI, USA aut NATIONALLICENCE 773 0- Journal of Oceanography Springer Japan 71/1(2015-02-01), 19-26 0916-8370 71:1<19 2015 71 10872