The Mindanao Current (MC), a low-latitude western boundary current in the Pacific Ocean, plays an important role in heat and freshwater transport to the western Pacific warm pool and the Indian Ocean. However, there have been relatively few comprehensive studies of the structure and variability of the MC and its connectivity to regional circulation. The Origins of the Kuroshio and Mindanao Current (OKMC) initiative combines four years of glider observations of the MC, a historical conductivity-temperature-depth (CTD)/float climatology, and results from a global strongly eddying forward ocean general circulation model simulation and a regional ocean state estimate. The MC is resolved as a strong southward current primarily within the upper 200 m, approaching 1 m s–1, and extending roughly 300 km offshore of Mindanao. Observations and model simulations show a persistent northward Mindanao Undercurrent (MUC) below the thermocline. The MC transports water masses of North Pacific origin southward, while the MUC carries water with South Pacific characteristics northward. The subthermocline transport of the MC and the MUC is connected to other undercurrents in the Philippine Sea. The variability of this transport is a topic of continuing research.

Schönau, M.C., D.L. Rudnick, I. Cerovecki, G. Gopalakrishnan, B.D. Cornuelle, J.L. McClean, and B. Qiu. 2015. The Mindanao Current: Mean structure and connectivity. Oceanography 28(4):34–45, https://doi.org/10.5670/oceanog.2015.79.

Bell, J.D. 2013. Mixed responses of tropical Pacific fisheries and aquaculture to climate change. Nature Climate Change 3(6):591–599, https://doi.org/10.1038/nclimate1838.

Bingham, F.M., and R. Lukas 1994. The southward intrusion of North Pacific Intermediate Water along the Mindanao coast. Journal of Physical Oceanography 24(1):141–154, https://doi.org/10.1175/1520-0485(1994)024​<0141:TSIONP>2.0.CO;2.

Bingham, F.M., and R. Lukas 1995. The distribution of intermediate water in the western equatorial Pacific during January–February 1986. Deep Sea Research Part I 42(9):1,545–1,573, https://doi.org/​10.1016/0967-0637(95)00064-D.

Davis, R.E., W.S. Kessler, and J.T. Sherman. 2012. Gliders measure western boundary current transport from the South Pacific to the equator. Journal of Physical Oceanography 42(11):2,001–2,013, https://doi.org/10.1175/JPO-D-12-022.1.

Dukowicz, J.K., and R.D. Smith 1994. Implicit free-surface method for the Bryan-Cox-Semtner ocean model. Journal of Geophysical Research 99(C4):7,991–8,014, https://doi.org/10.1029/93JC03455.

Ffield, A., and A.L. Gordon. 1992. Vertical mixing in the Indonesian thermocline. Journal of Physical Oceanography 22:184–195, https://doi.org/10.1175/1520-0485(1992)022​<0184:VMITIT>2.0.CO;2.

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(C12):25,063–25,080, https://doi.org/​10.1029/94JC02277.

Ganachaud, A., S. Cravatte, A. Melet, A. Schiller, N.J. Holbrook, B.M. Sloyan, M.J. Widlansky, M. Bowen, J. Verron, P. Wiles, and others. 2014. The Southwest Pacific Ocean circulation and climate experiment (SPICE). Journal of Geophysical Research 119(11):7,660–7,686, https://doi.org/​10.1002/2013JC009678.

Gordon, A.L. 1986. Interocean exchange of thermocline water. Journal of Geophysical Research 91(C4):5,037–5,046, https://doi.org/​10.1029/JC091iC04p05037.

Gouretski, V.V., and K.P. Koltermann. 2004. WOCE Global Hydrographic Climatology: A Technical Report, vol. 35. Bundesamtes für Seeschiffahrt und Hydrographie, Hamburg, Germany, 52 pp.

Gu, D., and S.G. Philander. 1997. Interdecadal climate fluctuations that depend on exchanges between the tropics and extratropics. Science 275:805–807, https://doi.org/10.1126/science.275.5301.805.

Heimbach, P., C. Hill, and R. Giering. 2002. Automatic generation of efficient adjoint code for a parallel Navier-Stokes solver. Computational Science—ICCS 2002, International Conference Amsterdam, The Netherlands, April 21–24, 2002, https://doi.org/10.1007/3-540-46080-2_107.

Hu, D., W. Cai, A. Ganachaud, W.S. Kessler, and J. Sprintall. 2015a. Introduction to special section on Western Pacific Ocean Circulation and Climate. Journal of Geophysical Research 120(5):3,175–3,176, https://doi.org/​10.1002/2015JC010856.

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

Hu, D.X., M.C. Cui, T.D. Qu, and Y.X. Li. 1991. A subsurface northward current off Mindanao identified by dynamic calculation. Oceanography of Asian Marginal Seas 54:359–365, https://doi.org/10.1016/S0422-9894(08)70108-9.

Kashino, Y. 2005. Variability of the Mindanao Current: Mooring observation results. Geophysical Research Letters 32, L18611, https://doi.org/​10.1029/2005GL023880.

Kashino, Y., A. Atmadipoera, Y. Kuroda, and Lukijanto. 2013. Observed features of the Halmahera and Mindanao eddies. Journal of Geophysical Research 118(12):6,543–6,560, https://doi.org/​10.1002/2013JC009207.

Kashino, Y., I. Ueki, and H. Sasaki. 2015. Ocean variability east of Mindanao: Mooring observations at 7°N, revisited. Journal of Geophysical Research 120:2,540–2,554, https://doi.org/​10.1002/2015JC010703.

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.-X., and O. Talagrand. 1986. Variational algorithms for analysis and assimilation of meteorological observations: Theoretical aspects. Tellus A 38A(2):97–110, https://doi.org/​10.1111/j.1600-0870.1986.tb00459.x.

Lindstrom, E., R. Lukas, R. Fine, E. Firing, S. Godfrey, G. Meyers, and M. Tsuchiya. 1987. The western equatorial Pacific Ocean circulation study. Nature 330:533–537, https://doi.org/​10.1038/330533a0.

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(C4):7,089–7,104, https://doi.org/10.1029/91JC00062.

Lukas, R., T. Yamagata, and J.P. McCreary. 1996. Pacific low-latitude western boundary currents and the Indonesian throughflow. Journal of Geophysical Research 101(C5):12,209–12,216, https://doi.org/10.1029/96JC01204.

Marshall, J., A. Adcroft, 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.

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(12):2,682–2,698, https://doi.org/10.1175/JPO-D-13-099.1.

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(C5):12,315–12,330, https://doi.org/​10.1029/95JC03204.

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.

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., T.-L. Chiang, C.-R. Wu, P. Dutrieux, and D. Hu. 2012. Mindanao Current/Undercurrent in an eddy-resolving GCM. Journal of Geophysical Research 117, C06026, https://doi.org/​10.1029/2011JC007838.

Qu, T., T. Kagimoto, and T. Yamagata. 1997. A subsurface countercurrent along the east coast of Luzon. Deep Sea Research Part I 44(3):413–423, https://doi.org/10.1016/S0967-0637(96)00121-5.

Qu, T., and R. Lukas. 2003. The bifurcation of the North Equatorial Current in the Pacific. Journal of Physical Oceanography 33(1):5–18, https://doi.org/10.1175/1520-0485(2003)033​<0005:TBOTNE>2.0.CO;2.

Qu, T., and E.J. Lindstrom. 2004. Northward intrusion of Antarctic Intermediate Water in the western Pacific. Journal of Physical Oceanography 34(9):2,104–2,118, https://doi.org/10.1175/1520-0485(2004)034​<2104:NIOAIW>2.0.CO;2.

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

Rudnick, D.L., S. Jan, and C.M. Lee. 2015. A new look at circulation in the western North Pacific. Oceanography 28(4):16–23, https://doi.org/10.5670/oceanog.2015.77.

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.

Sherman, J., R.E. Davis, W.B. Owens, and J. Valdes. 2001. The autonomous underwater glider “Spray.” IEEE Journal of Oceanic Engineering 26(4):437–446, https://doi.org/​10.1109/48.972076.

Smith, W.H.F., and D.T. Sandwell. 1997. Global seafloor topography from satellite altimetry and ship depth soundings. Science 277:1,957–1,962, https://doi.org/10.1126/science.277.5334.1956.

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(2):307–318, https://doi.org/10.1175/1520-0485(1990)020​<0307:OOTPNE>2.0.CO;2.

Tsuchiya, M. 1991. Flow path of the Antarctic Intermediate Water in the western equatorial South Pacific Ocean. Deep Sea Research Part A 38(Supplement 1):S273–S279, https://doi.org/10.1016/S0198-0149(12)80013-6.

Tsuchiya, M., R. Lukas, R.A. Fine, E. Firing, and E. Lindstrom. 1989. Source waters of the Pacific equatorial undercurrent. Progress in Oceanography 23(2):101–147, https://doi.org/10.1016/0079-6611(89)90012-8.

Wang, F., N. Zang, Y. Li, and D. Hu. 2015. On the subsurface countercurrents in the Philippine Sea. Journal of Geophysical Research 120:131–144, https://doi.org/10.1002/2013JC009690.

Wijffels, S.E., E. Firing, and J. Toole. 1995. The mean structure and variability of the Mindanao Current at 8°N. Journal of Geophysical Research 100(C9):18,421–18,435, https://doi.org/​10.1029/95JC01347.

Wunsch, C. 1996. The Ocean Circulation Inverse Problem. Cambridge University Press, Cambridge, UK, 458 pp., https://doi.org/10.1017/CBO9780511629570.

Wyrtki, K. 1961. Scientific results of marine investigations of the South China Sea and the Gulf of Thailand 1959–1961. NAGA Report, vol. 2. Scripps Institution of Oceanography, La Jolla, CA, http://escholarship.org/uc/item/49n9x3t4. 

Yang, Y.J., S. Jan, M.-H. Chang, J. Wang, V. Mensah, T.-H. Kuo, C.-J. Tsai, C.-Y. Lee, M. Andres, L.R. Centurioni, and others. 2015. Mean structure and fluctuations of the Kuroshio East of Taiwan from in situ and remote observations. Oceanography 28(4):74–83, https://doi.org/10.5670/oceanog.2015.83.

Zhang, L., D. Hu, S. Hu, F. Wang, F. Wang, and D. Yuan. 2014. Mindanao Current/Undercurrent measured by a subsurface mooring. Journal of Geophysical Research 119(6):3,617–3,628, https://doi.org/10.1002/2013JC009693.

Zhang, Y., W.B. Rossow, A.A. Lacis, V. Oinas, and M.I. Mishchenko. 2004. Calculation of radiative fluxes 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.

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