Journal of Oceanography

, Volume 70, Issue 4, pp 389–403 | Cite as

Origin of near-surface high-salinity water observed in the Kuroshio Extension region

  • Akira NaganoEmail author
  • Kazuyuki Uehara
  • Toshio Suga
  • Yoshimi Kawai
  • Hiroshi Ichikawa
  • Meghan F. Cronin
Short Contribution


Hydrographic data in the Kuroshio Extension (KE) region from 2008 to 2010 show large year-to-year variability in near-surface salinity, including a very large anomalous event in February 2010. During this event, the deep winter mixed layer in the southern KE region had higher salinity than had existed during the previous summer in September 2009. Our analysis shows that advection from the Philippine Sea along the western branch of the North Pacific subtropical gyre, taking approximately 9 months, resulted in this large salinity anomaly in February 2010 and contributes to the interannual salinity variability in the southern KE region.


Kuroshio Extension Salinity Sea surface buoy  Argo float KEO JKEO 



The authors thank the captains, crew, technicians, and scientists for collecting ship data on board the R/V Kaiyo, R/V Mirai, and R/V Syoyo-maru (cruise numbers: MR08-03, MR09-04, MR10-01 leg 2, MR10-06, KY09-07, and SY08-04), for the observations by KEO and K-TRITON (JKEO) buoy systems, and for special efforts by Drs. K. Matsumoto, M. Honda, and Y. Kashino. The authors also thank Drs. M. Konda, S. Hosoda, and T. Hasegawa for their helpful comments. Thanks are extended to anonymous reviewers for their helpful comments. This work was partly supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Grant-in-Aid for Scientific Research on Innovative Areas (22106007).


  1. Alexander MA, Deser C (1995) A mechanism for the recurrence of wintertime midlatitude SST anomalies. J Phys Oceanogr 25:122–137CrossRefGoogle Scholar
  2. Andres M, Wimbush M, Park J-H, Chang K-I, Lim B-H, Watts DR, Ichikawa H, Teague WJ (2008) Observations of Kuroshio flow variations in the East China Sea. J Geophys Res 113(C05013). doi: 10.1029/2007JC004200
  3. Bingham FM, Foltz GR, McPhaden MJ (2012) Characteristics of the seasonal cycle of surface layer salinity in the global ocean. Ocean Sci 8:915–929. doi: 10.5194/os-8-915-2012 CrossRefGoogle Scholar
  4. Bryden H, Imawaki S (2001) Ocean heat transport. In: Siedler H, Church J, Gould J (eds) Ocean circulation and climate: observing and modeling the global ocean. Academic, London, pp 455–474CrossRefGoogle Scholar
  5. Cronin MF et al (2013) Formation and erosion of the seasonal thermocline in the Kuroshio Extension Recirculation Gyre. Deep Sea Res II 85:62–74. doi: 10.1016/j.dsr2.2012.07.018 CrossRefGoogle Scholar
  6. Dai A, Wigley TML (2000) Global patterns of ENSO-induced precipitation. Geophys Res Lett 27(9):1283–1286. doi: 10.1029/1999GL011140 CrossRefGoogle Scholar
  7. de Boyer Montégut C, Madec G, Fischer AS, Lazar A, Iudicone D(2004) Mixed layer depth over the global ocean: an examination of profile data and a profile-based climatology. J Geophys Res 109(C12003). doi: 10.1029/2004JC002378
  8. Donohue K et al (2008) Program studies the Kuroshio Extension. EOS Trans AGU 89(17):161–162. doi: 10.1029/2008EO170002 CrossRefGoogle Scholar
  9. Horel JD, Wallace JM (1981) Planetary-scale atmospheric phenomena associated with the southern oscillation. Mon Weather Rev 109:813–829CrossRefGoogle Scholar
  10. Hosoda S, Ohira T, Nakamura T (2008) A monthly mean dataset of global oceanic temperature and salinity derived from Argo float observations. JAMSTEC Rep Res Dev 8:47–59CrossRefGoogle Scholar
  11. Howe PJ, Donohue KA, Watts R (2009) Stream-coordinate structure and variability of the Kuroshio Extension. Deep Sea Res I 56:1093–1116. doi: 10.1016/j.dsr.2009.03.007 CrossRefGoogle Scholar
  12. Jayne SR et al (2009) The Kuroshio Extension and its recirculation gyres. Deep Sea Res I 56:2088–2099. doi: 10.1016/j.dsr.2009.08.006 CrossRefGoogle Scholar
  13. Kawai H (1969) Statistical estimation of isotherms indicative of the Kuroshio axis. Deep Sea Res Suppl. 16:109–115Google Scholar
  14. Kawai H (1972) Hydrography of the Kuroshio Extension. In: Stommel H, Yoshida K (eds) Kuroshio—its physical aspects. University of Tokyo Press, Tokyo, pp 235–352Google Scholar
  15. Kelly KA (2004) The relationship between oceanic heat transport and surface fluxes in the western North Pacific: 1970–2000. J Clim 17:573–588CrossRefGoogle Scholar
  16. Kistler R et al (2001) The NCEP-NCAR 50-year reanalysis: monthly means CD-ROM and documentation. Bull Am Meteorol Soc 82:247–267CrossRefGoogle Scholar
  17. Konda M, Ichikawa H, Tomita H, Cronin MF (2010) Surface heat flux variations across the Kuroshio Extension as observed by surface flux buoys. J Clim 23(19):5206–5221. doi: 10.1175/2010JCLI3391.1 CrossRefGoogle Scholar
  18. Masuzawa J (1972) Water characteristics of North Pacific central region. In: Stommel H, Yoshida K (eds) Kuroshio—its physical aspects. University of Tokyo Press, Tokyo, pp 95–127Google Scholar
  19. Mizuno K, Watanabe T (1998) Preliminary results of in-situ XCTD/CTD comparison test. J Oceanogr 54:373–380CrossRefGoogle Scholar
  20. Nagano A, Ichikawa K, Ichikawa H, Konda M, Murakami K (2009) Synoptic flow structures in the confluence region of the Kuroshio and the Ryukyu Current. J Geophys Res 114(C06007). doi: 10.1029/2008JC005213
  21. Nagano A, Ichikawa K, Ichikawa H, Tomita H, Tokinaga H, Konda M (2010) Stable volume and heat transports of the North Pacific subtropical gyre revealed by identifying the Kuroshio in synoptic hydrography south of Japan. J Geophys Res 115(C09002). doi: 10.1029/2009JC005747
  22. Nagano A, Ichikawa H, Yoshikawa Y, Kizu S, Hanawa K (2012a) Variation of the southward interior flow of the North Pacific subtropical gyre, as revealed by a repeat hydrographic survey. J Oceanogr 68(2):361–368. doi: 10.1007/s10872-012-0102-3 CrossRefGoogle Scholar
  23. Nagano A, Ichikawa K, Ichikawa H, Yoshikawa Y, Konda M, Murakami K (2012b) Subsurface current structures east of the Amami-Oshima Island based on LADCP observation. J Adv Mar Sci Technol Soc 18(2):19–26Google Scholar
  24. Nagano A, Ichikawa K, Ichikawa H, Konda M, Murakami K (2013) Volume transports proceeding to the Kuroshio Extension region and recirculating in the Shikoku Basin. J Oceanogr 69(3):285–293. doi: 10.1007/s10872-013-0173-9 CrossRefGoogle Scholar
  25. Nitani H (1972) Beginning of the Kuroshio. In: Stommel H, Yoshida K (eds) Kuroshio—its physical aspects. University of Tokyo Press, Tokyo, pp 129–163Google Scholar
  26. Oka E (2009) Seasonal and interannual variation of North Pacific subtropical mode water in 2003–2006. J Oceanogr 65:151–164CrossRefGoogle Scholar
  27. Oka E, Qiu B (2012) Progress of North Pacific mode water research in the past decade. J Oceanogr 68:5–12. doi: 10.1007/s10872-011-0032-5 CrossRefGoogle Scholar
  28. Okuda K, Yasuda I, Hiroe Y, Shimizu Y (2001) Structure of subsurface intrusion of the Oyashio water into the Kuroshio Extension and formation process of the North Pacific intermediate water. J Oceanogr 57:121–140CrossRefGoogle Scholar
  29. Qiu B, Chen S (2010) Interannual-to-decadal variability in the bifurcation of the North Equatorial Current off the Philippines. J Phys Oceanogr 40:2525–2538. doi: 10.1175/2010JPO4462.1 CrossRefGoogle Scholar
  30. Rainville L, Jayne SR, Cronin MF (2014) Variations of the North Pacific subtropical mode water from direct observations. J Clim 27:2842–2860. doi: 10.1175/JCLI-D-13-00227.1 CrossRefGoogle Scholar
  31. Suga T, Hanawa K (1995) The subtropical mode water circulation in the North Pacific. J Phys Oceanogr 25:958–970CrossRefGoogle Scholar
  32. Suga T, Takei Y, Hanawa K (1997) Thermostad distribution in the North Pacific subtropical gyre: the central mode water and the subtropical mode water. J Phys Oceanogr 27(1):140–152CrossRefGoogle Scholar
  33. Suga T, Kato A, Hanawa K (2000) North Pacific Tropical Water: its climatology and temporal changes associated with the climate regime shift in the 1970s. Prog Oceanogr 47:223–256CrossRefGoogle Scholar
  34. Sugimoto S, Hanawa K (2005) Remote reemergence areas of winter sea surface temperature anomalies in the North Pacific. Geophys Res Lett 32(L01606). doi: 10.1029/2004GL021410
  35. Sugimoto S, Takahashi N, Hanawa K (2013) Marked freshening of North Pacific subtropical mode water in 2009 and 2010: influence of freshwater supply in the 2008 warm season. Geophys Res Lett 40:3102–3105. doi: 10.1002/grl.50600 CrossRefGoogle Scholar
  36. Taft B (1978) Structure of Kuroshio south of Japan. J Mar Res 36:77–117Google Scholar
  37. Tomita H, Kubota M, Cronin MF, Iwasaki S, Konda M, Ichikawa H (2010) An assessment of the surface turbulent heat fluxes from J-OFURO2 at the KEO and JKEO sites. J Geophys Res 115(C03018). doi: 10.1029/2009JC005545
  38. Vivier F, Kelly KA, Thompson L (2002) Heat budget in the Kuroshio Extension region: 1993–99. J Phys Oceanogr 32:3436–3454CrossRefGoogle Scholar

Copyright information

© The Oceanographic Society of Japan and Springer Japan 2014

Authors and Affiliations

  • Akira Nagano
    • 1
    Email author
  • Kazuyuki Uehara
    • 2
  • Toshio Suga
    • 1
    • 3
  • Yoshimi Kawai
    • 1
  • Hiroshi Ichikawa
    • 1
  • Meghan F. Cronin
    • 4
  1. 1.Research and Development Center for Global ChangeJapan Agency for Marine-Earth Science and TechnologyYokosukaJapan
  2. 2.School of Marine Science and TechnologyTokai UniversityShimizuJapan
  3. 3.Graduate School of ScienceTohoku UniversitySendaiJapan
  4. 4.Pacific Marine Environmental LaboratoryNational Oceanic and Atmospheric AdministrationSeattleUSA

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