Journal of Oceanography

, Volume 68, Issue 3, pp 439–452 | Cite as

Spreading and salinity change of North Pacific Tropical Water in the Philippine Sea

Original Article


Newly formed North Pacific Tropical Water (NPTW) is carried to the Philippine Sea (PS) by the North Equatorial Current (NEC) as a subsurface salinity maximum. In this study its spreading and salinity change processes are explored using existing hydrographic data of the World Ocean Database 2009 and Argo floats. Spreading of NPTW is closely associated with the transports of the NEC, Mindanao Current (MC), and Kuroshio. Estimated for subsurface water with salinity S greater than 34.8 psu, the southward (northward) geostrophic transport of NPTW by the MC (Kuroshio) at 8°N (18°N) is about 4.4 (5.7) Sv (1 Sv = 106 m3 s−1), which is not sensitive to reference level choice. Fields of salinity maximum, geostrophic current, sea level variation, and potential vorticity suggest that the equatorward spreading of NPTW to the tropics is primarily afforded by the MC, whereas its poleward spreading is achieved by both the Kuroshio transport along the coast and open-ocean mesoscale eddy fluxes in the northern PS. The NPTW also undergoes a prominent freshening in the PS. Lying beneath fresh surface water, salinity decreases quicker in the upper part of the NPTW, which gradually lowers the salinity maximum of NPTW to denser isopycnals. Salinity decrease is especially fast in the MC, with along-path decreasing rate reaching O (10−7 psu s−1). Both diapycnal and isopycnal mixing effects are shown to be elevated in the MC owing to enhanced salinity gradient near the Mindanao Eddy. These results suggest intensive dispersion of thermal anomalies along the subtropical-to-tropical thermocline water pathway near the western boundary.


North Pacific Tropical Water Philippine Sea NEC bifurcation Mesoscale eddies Mixing Kuroshio Mindanao current 


  1. Balmaseda MA, Vidard A, Anderson DLT (2008) The ECMWF ocean analysis system: ORA-S3. Mon Weather Rev 136:3018–3034CrossRefGoogle Scholar
  2. Bingham F, Lukas R (1994) The southward intrusion of North Pacific intermediate water along the Mindanao coast. J Phys Oceanogr 24:141–154CrossRefGoogle Scholar
  3. Boyer TP et al (2009) World ocean database 2009. In: Levitus S (ed) NOAA Atlas NESDIS 66. US Government Printing Office, Washingon, 216 pp, DVDsGoogle Scholar
  4. Cannon GA (1966) Tropical waters in the western Pacific Oceans, August–September 1957. Deep Sea Res 13:1139–1148Google Scholar
  5. Chelton DB, Schlax MG, Samelson RM (2011) Global observations of nonlinear mesoscale eddies. Progr Oceanogr 91:167–216CrossRefGoogle Scholar
  6. Chen Z, Wu L (2011) Dynamics of the seasonal variation of the North Equatorial Current bifurcation. J Geophys Res 116:C02018. doi:10.1029/2010JC006664 CrossRefGoogle Scholar
  7. Ducet N, Le Traon P, Reverdin G (2000) Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and-2. J Geophys Res 105(C8):19477–19498CrossRefGoogle Scholar
  8. Fine RA, Lukas R, Bingham FM, Warner MJ, Gammon RH (1994) The western equatorial Pacific: a water mass crossroads. J Geophys Res 99(C12):25063–25080CrossRefGoogle Scholar
  9. Goodman PJ, Hazeleger W, de Vries P, Cane M (2005) Pathways into the Pacific Equatorial Undercurrent: a trajectory analysis. J Phys Oceanogr 35:2134–2151CrossRefGoogle Scholar
  10. Gordon AL (1986) Interocean exchange of thermocline water. J Geophys Res 91(C4):5037–5046CrossRefGoogle Scholar
  11. Gould J, The Argo steering team (2004) Argo profiling floats bring new era of in situ ocean observations. Eos Trans AGU 85(19):185. doi:10.1029/2004EO190002 CrossRefGoogle Scholar
  12. Gouriou Y, Toole J (1993) Mean circulation of the upper layers of the western equatorial Pacific Ocean. J Geophys Res 98:22495–22520CrossRefGoogle Scholar
  13. Gu D, Philander SGH (1997) Interdecadal climate fluctuations that depend on exchange between the tropics and extratropics. Science 275:805–807CrossRefGoogle Scholar
  14. Guan B (1983) Major features of warm and cold eddies south of Nansei Islands. Chin J Oceanol Limol 1:248–257CrossRefGoogle Scholar
  15. Jia F, Wu L, Qiu B (2011) Seasonal modulation of eddy kinetic energy and its formation mechanism in the southeast Indian Ocean. J Phys Oceanogr 41:657–665CrossRefGoogle Scholar
  16. Joyce TM, Luyten JR, Kubryakov A, Bahr FB, Pallant JS (1998) Meso-to large-scale structure of subducting water in the subtropical gyre of the eastern North Atlantic Ocean. J Phys Oceanogr 28:40–61CrossRefGoogle Scholar
  17. Kashino Y, Aoyama M, Kawano T, Hendiarti N, Syaefudin, Anantasena Y, Muneyama K, Watanabe H (1996) The water masses between Mindanao and New Guinea. J Geophys Res 101:12391–12400CrossRefGoogle Scholar
  18. Kashino Y, Ishida A, Hosoda S (2011) Observed ocean variability in the Mindanao Dome region. J Phys Oceanogr 41:287–302CrossRefGoogle Scholar
  19. Kim YY, Qu T, Jensen T, Miyama T, Mitsudera H, Kang HW, Ishida A (2004) Seasonal and interannual variations of the North Equatorial Current bifurcation in a high-resolution OGCM. J Geophys Res 109(C3):C03040. doi:10.01029/2003JC002013 CrossRefGoogle Scholar
  20. Lukas R, Lindstrom E (1991) The mixed layer of the western equatorial Pacific Ocean. J Geophys Res 96:3343–3358CrossRefGoogle Scholar
  21. Lukas R, Firing E, Hacker P, Richardson PL, Collins CA, Fine R, Gammon RH (1991) Observations of the Mindanao Current during the Western Equatorial Pacific Ocean Circulation Study. J Geophys Res 96(C4):7089–7104CrossRefGoogle Scholar
  22. Lukas R, Yamagata T, McCreary JP (1996) Pacific low-latitude western boundary currents and the Indonesian throughflow. J Geophys Res 101(C5):12209–12216CrossRefGoogle Scholar
  23. Masumoto Y, Yamagata T (1991) Response of the western tropical Pacific to the Asian winter monsoon: the generation of the Mindanao Dome. J Phys Oceanogr 21:1386–1398CrossRefGoogle Scholar
  24. Masuzawa J (1969) Subtropical mode water. Deep Sea Res 16:463–472Google Scholar
  25. McCreary JP, Lu P (1994) On the interaction between the subtropical and the equatorial oceans: the subtropical cell. J Phys Oceanogr 24:466–497Google Scholar
  26. McDougall TJ (1984) The relative roles of diapycnal and isopycnal mixing on subsurface water mass conversion. J Phys Oceanogr 14:1577–1589CrossRefGoogle Scholar
  27. O’Connor BM, Fine RA, Maillet KA, Olson DB (2002) Formation rates of subtropical underwater in the Pacific Ocean. Deep Sea Res Part I 49:1571–1590CrossRefGoogle Scholar
  28. Qiu B (1999) Seasonal eddy field modulation of the North Pacific Subtropical Countercurrent: TOPEX/Poseidon observations and theory. J Phys Oceanogr 29:2471–2486CrossRefGoogle Scholar
  29. Qiu B, Chen S (2005) Eddy-induced heat transport in the subtropical North Pacific from Argo, TMI, and altimetry measurements. J Phys Oceanogr 35:458–473CrossRefGoogle Scholar
  30. Qiu B, Chen S (2010a) Interannual-to-decadal variability in the bifurcation of the North Equatorial Current off the Philippines. J Phys Oceanogr 40:2525–2538CrossRefGoogle Scholar
  31. Qiu B, Chen S (2010b) Interannual variability of the North Pacific Subtropical Countercurrent and its associated mesoscale eddy field. J Phys Oceanogr 40:213–225CrossRefGoogle Scholar
  32. Qiu B, Chen S (2012) Multidecadal sea level and gyre circulation variability in the Northwestern Tropical Pacific Ocean. J Phys Oceanogr 42:193–206CrossRefGoogle Scholar
  33. Qiu B, Joyce TM (1992) Interannual variability in the mid- and low-latitude Western North Pacific. J Phys Oceanogr 22:1062–1084CrossRefGoogle Scholar
  34. Qiu B, Lukas R (1996) Seasonal and interannual variability of the North Equatorial Current, the Mindanao Current and the Kuroshio along the Pacific western boundary. J Geophys Res 101(C5):12315–12330CrossRefGoogle Scholar
  35. Qu T, Lukas R (2003) The bifurcation of the North Equatorial Current in the Pacific. J Phys Oceanogr 33:5–18CrossRefGoogle Scholar
  36. Qu T, Mitsudera H, Yamagata T (1998) On the western boundary currents in the Philippine Sea. J Geophys Res 103(C4):7537–7548CrossRefGoogle Scholar
  37. Qu T, Mitsudera H, Yamagata T (1999) A climatology of the circulation and water masses distribution near the Philippine coast. J Phys Oceanogr 39:1488–1505CrossRefGoogle Scholar
  38. Qu T, Mitsudera H, Yamagata T (2000) Intrusion of the North Pacific waters into the South China Sea. J Geophys Res 105(C3):6415–6424CrossRefGoogle Scholar
  39. Roemmich D, Gilson J (2001) Eddy transport of heat and thermocline waters in the North Pacific: a key to interannual/decadal climate variability? J Phys Oceanogr 31:675–687CrossRefGoogle Scholar
  40. Roemmich D et al (2009) The Argo program: observing the global ocean with profiling floats. Oceanography 22:34–43CrossRefGoogle Scholar
  41. Schneider N, Miller AJ, Alexander MA, Deser C (1999) Subduction of decadal North Pacific temperature anomalies: observations and dynamics. J Phys Oceanogr 29:1056–1070CrossRefGoogle Scholar
  42. Sprintall J, McPhaden MJ (1994) Surface layer variations observed in multiyear time series measurements from the western equatorial Pacific. J Geophys Res 99(C1):963–979CrossRefGoogle Scholar
  43. 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
  44. Toole JM, Millard R, Wang Z, Pu S (1990) Observations of the Pacific North Equatorial Current Bifurcation at the Philippine Coast. J Phys Oceanogr 20:307–318CrossRefGoogle Scholar
  45. Tsuchiya M (1968) Upper waters of the intertropical Pacific Ocean: Johns Hopkins Oceanographic Studies, vol 4. Johns Hopkins University Press, Baltimore, p 50Google Scholar
  46. Tsuchiya M (1991) Flow path of the Antarctic Intermediate Water in the western equatorial South Pacific Ocean. Deep Sea Res Part A 38:273–279Google Scholar
  47. Yang D, Yin B, Liu Z, Bai T, Qi J, Chen H (2012) Numerical study on the pattern and origins of Kuroshio branches in the bottom water of southern East China Sea in summer. J Geophys Res 117:C02014. doi:10.1029/2011JC007528 CrossRefGoogle Scholar
  48. Yaremchuk M, Qu T (2004) Seasonal variability of the large-scale currents near the coast of the Philippines. J Phys Oceanogr 34:844–855CrossRefGoogle Scholar

Copyright information

© The Oceanographic Society of Japan and Springer 2012

Authors and Affiliations

  1. 1.Key Laboratory of Ocean Circulation and WavesInstitute of Oceanology, Chinese Academy of SciencesQingdaoChina
  2. 2.Graduate University of Chinese Academy of SciencesBeijingChina

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