Oceanography The Official Magazine of
The Oceanography Society
Volume 28 Issue 04

View Issue TOC
Volume 28, No. 4
Pages 24 - 33

The Pacific North Equatorial Current: New Insights from the Origins of the Kuroshio and Mindanao Currents (OKMC) Project

Bo Qiu Daniel L. RudnickIvana CeroveckiBruce D. CornuelleShuiming ChenMartha C. SchönauJulie L. McCleanGanesh Gopalakrishnan
Article Abstract

Located at the crossroads of the tropical and subtropical circulations, the westward-flowing North Equatorial Current (NEC) and its subsequent bifurcation off the Philippine coast near 13°N serve as important pathways for heat and water mass exchanges between the mid- and low-latitude North Pacific Ocean. Because the western Pacific warm pool, with sea surface temperatures >28°C, extends poleward of 17°N in the western North Pacific, the bifurcation and transport partitioning of the NEC into the Kuroshio and Mindanao Currents are likely to affect the temporal evolution of the warm pool through lateral advection. In addition to its influence on physical conditions, NEC variability is also important to the regional biological properties and the fisheries along the Philippine coast and in the western Pacific Ocean. This article synthesizes our current understandings of the NEC, especially those garnered through the recent Origins of the Kuroshio and Mindanao Current (OKMC) project.


Qiu, B., D.L. Rudnick, I. Cerovecki, B.D. Cornuelle, S. Chen, M.C. Schönau, J.L. McClean, and G. Gopalakrishnan. 2015. The Pacific North Equatorial Current: New insights from the origins of the Kuroshio and Mindanao Currents (OKMC) Project. Oceanography 28(4):24–33, https://doi.org/10.5670/oceanog.2015.78.


Chassignet, E.P., H.E. Hurlburt, O.M. Smedstad, G.R. Halliwell, P.J. Hogan, A.J. Wallcraft, R. Baraille, and R. Bleck. 2007. The HYCOM (HYbrid Coordinate Ocean Model) data assimilative system. Journal of Marine Systems 65:60–83, https://doi.org/10.1016/j.jmarsys.2005.09.016.

Delman, A.S., J.L. McClean, J. Sprintall, L.D. Talley, and E. Yulaeva. 2015. Effects of eddy vorticity forcing on the mean state of the Kuroshio Extension. Journal of Physical Oceanography 45:1,356–1,375, https://doi.org/10.1175/JPO-D-13-0259.1.

Dukowicz, J.K., and R.D. Smith. 1994. Implicit free-​surface method for the Bryan-Cox-Semtner ocean model. Journal of Geophysical Research 99:7,991–8,014, https://doi.org/​10.1029/93JC03455.

Fine, R.A., R. Lukas, F.M. Bingham, M.J. Warner, and R.H. Gammon. 1994. The western equatorial Pacific: A water mass crossroads. Journal of Geophysical Research 99:25,063–25,080, https://doi.org/​10.1029/94JC02277.

Gordon, A.L., P. Flament, C. Villanoy, and L. Centurioni. 2014. The nascent Kuroshio of Lamon Bay. Journal of Geophysical Research 119:4,251–4,263, https://doi.org/​10.1002/2014JC009882.

Heimbach, P., C. Hill, and R. Giering. 2002. Automatic generation of efficient adjoint code for a parallel Navier-Stokes solver. Pp. 1,019–1,028 in Proceedings of the International Conference on Computational Science-ICCS 2002, Amsterdam, The Netherlands, vol. 230, Part II, Springer-Verlag.

Hu, D., L. Wu, W. Cai, A. Sen Gupta, A. Ganachaud, B. Qiu, A.L. Gordon, X. Lin, Z. Chen, S. Hu, and others. 2015. Pacific western boundary currents and their roles in climate. Nature 522:299–308, https://doi.org/10.1038/nature14504.

Huang, R.X., and B. Qiu. 1994. Three-dimensional structure of the wind-driven circulation in the subtropical North Pacific. Journal of Physical Oceanography 24:1,608–1,622, https://doi.org/10.1175/1520-0485(1994)024​<1608:TDSOTW>2.0.CO;2.

Jin, F.-F. 1997. An equatorial ocean recharge paradigm for ENSO: Part I. Conceptual model. Journal of the Atmospheric Sciences 54:811–829, https://doi.org/10.1175/1520-0469(1997)054​<0811:AEORPF>2.0.CO;2.

Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Sana, G. White, J. Woollen, and others. 1996. The NCEP/NCAR 40 reanalysis project. Bulletin of the American Meteorological Society 77:437–471, https://doi.org/10.1175/1520-0477(1996)077​<0437:TNYRP>2.0.CO;2.

Kessler, W.S. 1990. Observations of long Rossby waves in the northern tropical Pacific. Journal of Geophysical Research 95:5,183–5,217, https://doi.org/10.1029/JC095iC04p05183.

Kim, Y., T. Qu, T. Jensen, T. Miyama, H. Mitsudera, H.-W. Kang, and A. Ishida. 2004. Seasonal and interannual variations of the North Equatorial Current bifurcation in a high-resolution OGCM. Journal of Geophysical Research 109, C03040, https://doi.org/10.1029/2003JC002013.

Kobashi, F., and H. Kawamura. 2002. Seasonal variation and instability nature of the North Pacific Subtropical Countercurrent and the Hawaiian Lee Countercurrent. Journal of Geophysical Research 107, C03185, https://doi.org/10.1029/2001JC001225.

Large, W., and S. Pond. 1981. Open ocean momentum flux measurements in moderate to strong winds. Journal of Physical Oceanography 11:324–336, https://doi.org/10.1175/1520-0485(1981)011​<0324:OOMFMI>2.0.CO;2.

Large, W.G., and S.G. Yeager. 2009. The global climatology of an interannually varying air-sea flux data set. Climate Dynamics 33:341–364, https://doi.org/​10.1007/s00382-008-0441-3.

Le Dimet, F., and O. Talagrand. 1986. Variational algorithms for analysis and assimilation of meteorological observations: Theoretical aspects. Tellus A 38:97–110, https://doi.org/​10.1111/​j.1600-0870.1986.tb00459.x.

Lukas, R., E. Firing, P. Hacker, P.L. Richardson, C.A. Collins, R. Fine, and R. Gammon. 1991. Observations of the Mindanao Current during the Western Equatorial Pacific Ocean Circulation Study. Journal of Geophysical Research 96:7,089–7,104, https://doi.org/10.1029/91JC00062.

Maltrud, M.E., F.O. Bryan, and S. Peacock. 2010. Boundary impulse response functions in a century-long eddying global ocean simulation. Environmental Fluid Mechanics 10:275–295, https://doi.org/10.1007/s10652-009-9154-3.

Marshall, J., A. Adcroft, C. Hill, L. Perelman, and C. Heisey. 1997. A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers. Journal of Geophysical Research 102:5,753–5,766, https://doi.org/​10.1029/96JC02775.

McClean, J.L., D.C. Bader, F.O. Bryan, M.E. Maltrud, J.M. Dennis, A.A. Mirin, P.W. Jones, Y-.Y. Kim, D.P. Ivanova, M. Vertenstein, and others. 2011. A prototype two-decade fully-​coupled fine-​resolution CCSM simulation. Ocean Modelling 39:10–30, https://doi.org/10.1016/​j.ocemod.2011.02.011.

Nan, F., H. Xue, F. Chai, D. Wang, F. Yu, M. Shi, P. Guo, and P. Xiu. 2013. Weakening of the Kuroshio intrusion into the South China Sea over the past two decades. Journal of Climate 26:8,097–8,110, https://doi.org/10.1175/JCLI-D-12-00315.1.

Nitani, H. 1972. Beginning of the Kuroshio. Pp. 129–163 in Kuroshio: Physical Aspects of the Japan Current. H. Stommel and K. Yashida, eds, University of Washington Press, Seattle.

Pedlosky, J. 1987. Geophysical Fluid Dynamics. Springer-Verlag, 710 pp.

Qiu, B. 1999. Seasonal eddy field modulation of the North Pacific Subtropical Countercurrent: TOPEX/POSEIDON observations and theory. Journal of Physical Oceanography 29:2,471–2,486, https://doi.org/10.1175/1520-0485(1999)029​<2471:SEFMOT>2.0.CO;2.

Qiu, B., and S. Chen. 2010. Interannual-to-decadal variability in the bifurcation of the North Equatorial Current off the Philippines. Journal of Physical Oceanography 40:2,525–2,538, https://doi.org/​10.1175/2010JPO4462.1.

Qiu, B., S. Chen, D.L. Rudnick, Y. Kashino. 2015a. A new paradigm for the North Pacific subthermocline low-latitude western boundary current system. Journal of Physical Oceanography 45:2,407–2,423, https://doi.org/​10.1175/JPO-D-15-0035.1.

Qiu, B., S. Chen, and H. Sasaki. 2013a. Generation of the North Equatorial Undercurrent jets by triad baroclinic Rossby wave interactions. Journal of Physical Oceanography 43:2,682–2,698, https://doi.org/10.1175/JPO-D-13-099.1.

Qiu, B., S. Chen, L. Wu, and S. Kida. 2015b. Wind- versus eddy-forced regional sea level trends and variability in the North Pacific Ocean. Journal of Climate 28:1,561–1,577, https://doi.org/10.1175/JCLI-D-14-00479.1.

Qiu, B., and T.M. Joyce. 1992. Interannual variability in the mid- and low-latitude western North Pacific. Journal of Physical Oceanography 22:1,062–1,079, https://doi.org/10.1175/1520-0485(1992)022​<1062:IVITMA>2.0.CO;2.

Qiu, B., and R. Lukas. 1996. Seasonal and interannual variability of the North Equatorial Current, the Mindanao Current, and the Kuroshio along the Pacific western boundary. Journal of Geophysical Research 101:12,315–12,330, https://doi.org/​10.1029/95JC03204.

Qiu, B., M. Mao, and Y. Kashino. 1999. Intraseasonal variability in the Indo-Pacific Throughflow and the regions surrounding the Indonesian Seas. Journal of Physical Oceanography 29:1,599–1,618, https://doi.org/10.1175/1520-0485(1999)029​<1599:IVITIP>2.0.CO;2.

Qiu, B., D.L. Rudnick, S. Chen, and Y. Kashino. 2013b. Quasi-stationary North Equatorial Undercurrent jets across the tropical North Pacific Ocean. Geophysical Research Letters 40:2,183–2,187, https://doi.org/10.1002/grl.50394.

Qu, T., J. Gan, A. Ishida, Y. Kashino, and T. Tozuka. 2008. Semiannual variation in the western tropical Pacific Ocean. Geophysical Research Letters 35, L16602, https://doi.org/10.1029/2008GL035058.

Qu, T., and R. Lukas. 2003. The bifurcation of the North Equatorial Current in the Pacific. Journal of Physical Oceanography 33:5–18, https://doi.org/10.1175/1520-0485(2003)033​<0005:TBOTNE>2.0.CO;2.

Qu, T., H. Mitsudera, and T. Yamagata. 1998. On the western boundary currents in the Philippine Sea, Journal of Geophysical Research 103:7,537–7,548, https://doi.org/10.1029/98JC00263.

Rio, M.H., S. Guinehut, and G. Larnicol. 2011. New CNES-CLS09 global mean dynamic topography computed from the combination of GRACE data, altimetry, and in situ measurements. Journal of Geophysical Research 116, C07018, https://doi.org/10.1029/2010JC006505.

Risien, C.M., and D.B. Chelton. 2008. A global climatology of surface wind and wind stress fields from eight years of QuikSCAT scatterometer data. Journal of Physical Oceanography 38:2,379–2,413, https://doi.org/10.1175/2008JPO3881.1.

Roemmich, D., and J. Gilson. 2001. Eddy transport of heat and thermocline waters in the North Pacific: A key to interannual/decadal climate variability? Journal of Physical Oceanography 31:675–687, https://doi.org/10.1175/1520-0485(2001)031​<0675:ETOHAT>2.0.CO;2.

Roemmich, D., and J. Gilson. 2009. The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. Progress in Oceanography 82:81–100, https://doi.org/10.1016/j.pocean.2009.03.004.

Sasaki, Y.N., N. Schneider, N. Maximenko, K. Lebedev. 2010. Observational evidence for propagation of decadal spiciness anomalies in the North Pacific. Geophysical Research Letters 37, L07708, https://doi.org/10.1029/2010GL042716.

Schönau, M.C., and D.L. Rudnick. 2015. Glider observations of the North Equatorial Current in the western tropical Pacific. Journal of Geophysical Research 120:3,586–3,605, https://doi.org/​10.1002/2014JC010595.

Stammer, D., C. Wunsch, R. Giering, C. Eckert, P. Heimbach, J. Marotzke, A. Adcroft, C. Hill, and J. Marshall. 2002. Global ocean circulation during 1992–1997, estimated from ocean observations and a general circulation model. Journal of Geophysical Research 107(C9), 3118, https://doi.org/10.1029/2001JC000888.

Todd, R.E., D.L. Rudnick, M.R. Mazloff, R.E. Davis, and B.D. Cornuelle. 2011. Poleward flows in the southern California Current System: Glider observations and numerical simulation. Journal of Geophysical Research 116, C02026, https://doi.org/10.1029/2010JC006536.

Toole, J.M., R.C. Millard, Z. Wang, and S. Pu. 1990. Observations of the Pacific North Equatorial Current bifurcation at the Philippine coast. Journal of Physical Oceanography 20:307–318, https://doi.org/10.1175/1520-0485(1990)020​<0307:OOTPNE>2.0.CO;2.

Toole, J.M., E. Zou, and R.C. Millard. 1988. On the circulation of the upper waters in the western equatorial Pacific Ocean. Deep Sea Research Part A 35:1,451–1,482, https://doi.org/​10.1016/0198-0149(88)90097-0.

Vianna, M.L., and V.V. Menezes. 2010. Mean mesoscale global ocean currents from geodetic pre-GOCE MDTs with a synthesis of the North Pacific circulation. Journal of Geophysical Research 115, C02016, https://doi.org/10.1029/2009JC005494.

Wunsch, C. 1996. The Ocean Circulation Inverse Problem. Cambridge University Press, Cambridge, UK, 458 pp.

Wyrtki, K. 1974. Sea level and the seasonal fluctuations of the equatorial currents in the western Pacific Ocean. Journal of Physical Oceanography 4:91–103, https://doi.org/10.1175/​1520-0485(1974)004<0091:SLATSF>2.0.CO;2.

Wyrtki, K., and B. Kilonsky. 1984. Mean water and current structure during the Hawaii-to-Tahiti Shuttle Experiment. Journal of Physical Oceanography 14:242–254, https://doi.org/​10.1175/1520-0485(1984)014​<0242:MWACSD>2.0.CO;2.

Yaremchuk, M., and T. Qu. 2004. Seasonal variability of the circulation near the Philippine coast. Journal of Physical Oceanography 34:844–855, https://doi.org/10.1175/1520-0485(2004)034​<0844:SVOTLC>2.0.CO;2.

Zhang, Y., W. Rossow, A. Lacis, V. Oinas, and M. Mishchenko. 2004. Calculation of radiative flux profiles from the surface to top-of-​atmosphere based on ISCCP and other global data sets: Refinements of the radiative transfer model and the input data. Journal of Geophysical Research 109, D19105, https://doi.org/10.1029/2003JD004457.

Zhuang, W., B. Qiu, and Y. Du. 2013. Low-frequency western Pacific Ocean sea level and circulation changes due to the connectivity of the Philippine archipelago. Journal of Geophysical Research 118:6,759–6,773, https://doi.org/​10.1002/2013JC009376.