a off Eastern Luzon, Philippines, Associated with the North Equatorial Current Bifurcation Latitude”/>
Oceanography The Official Magazine of
The Oceanography Society
Volume 28 Issue 04

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Volume 28, No. 4
Pages 46 - 53

Shifts in Chlorophyll a off Eastern Luzon, Philippines, Associated with the North Equatorial Current Bifurcation Latitude

Olivia C. Cabrera Cesar L. VillanoyIrene D. Alabia Arnold L. Gordon
Article Abstract

The circulation pattern off the east coast of Luzon, Philippines, as observed during two oceanographic cruises conducted in May/June 2011 and April/May 2012, features a northward-flowing current (the nascent Kuroshio) bracketed by an anticyclonic eddy to its northeast and a cyclonic eddy to its southwest. A previous study showed that a more northerly location of the North Equatorial Current (NEC) bifurcation during the 2011 cruise resulted in entrainment of more subtropical water from the Kuroshio into upper thermocline waters, while a more southerly bifurcation location during the 2012 cruise injected more tropical NEC water into upper thermocline waters offshore of eastern Luzon. Here, we show that the change in source of upper thermocline waters in this region can also be recognized in the distribution pattern of chlorophyll a. Horizontally averaged chlorophyll a profiles showed higher concentrations in the upper 125 m of the water column during the 2011 cruise when the bifurcation latitude was 13°N–14°N than during the 2012 cruise when the bifurcation latitude was observed at 10°N–11°N. Chlorophyll a data overlain on regional currents show that the 2011 nascent Kuroshio had a higher chlorophyll a content, supplied by the Kuroshio recirculation from the north, while the increased NEC content of the 2012 nascent Kuroshio was accompanied by reduced chlorophyll a within the upper thermocline, supporting the notion that horizontal advection plays an important role in chlorophyll variability off eastern Luzon. Using sea surface height anomalies as a proxy for upper ocean heat content, we show that warmer waters from the NEC supply the nascent Kuroshio when the location of the NEC bifurcation is more southerly. Empirical orthogonal function analysis of Moderate Resolution Imaging Spectroradiometer chlorophyll a data from 2003 to 2013 shows that the primary mode of chlorophyll a variability offshore of eastern Luzon was positively correlated with the NEC bifurcation latitude, further establishing that warmer, oligotrophic waters from the NEC supply the nascent Kuroshio when NEC bifurcation is southerly.

Citation

Cabrera, O.C., C.L. Villanoy, I.D. Alabia, and A.L. Gordon. 2015. Shifts in chlorophyll a off eastern Luzon, Philippines, associated with the North Equatorial Current bifurcation latitude. Oceanography 28(4):46–53, https://doi.org/10.5670/oceanog.2015.80.

References

Chang, Y.L., and L.Y. Oey. 2014. Analysis of STCC eddies using the Okubo-Weiss parameter on model and satellite data. Ocean Dynamics 64(2):259–271, https://doi.org/10.1007/s10236-013-0680-7

Chelton, D.B., P. Gaube, M.G. Schlax, J.J. Early, and R.M. Samelson. 2011. The influence of nonlinear mesoscale eddies on near-surface oceanic chlorophyll. Science 334:328–332, https://doi.org/​10.1126/science.1208897.

Furuya, K. 1990. Subsurface chlorophyll maximum in the tropical and subtropical western Pacific Ocean: Vertical profiles of phytoplankton biomass and its relationship with chlorophyll a and particulate carbon. Marine Biology 539:529–539, https://doi.org/10.1007/BF01313438.

Garcia, C., and V. Garcia. 2008. Variability of chlorophyll-a from ocean color images in the La Plata continental shelf region. Continental Shelf Research 28(13):1,568–1,578, https://doi.org/​10.1016/j.csr.2007.08.010.

Gaube, P., D.B. Chelton, R.M. Samelson, M.G. Schlax, and L.W. O’Neill. 2014. Satellite observations of mesoscale eddy-induced Ekman pumping. Journal of Physical Oceanography 45:104–132, https://doi.org/10.1175/JPO-D-14-0032.1.

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.

Kashino, Y., N. Espana, F. Syamsudin, K.J. Richards, T. Jensen, P. Dutrieux, and A. Ishida. 2009. Observations of the North Equatorial Current, Mindanao Current, and Kuroshio current system during the 2006/07 El Niño and 2007/08 La Niña. Journal of Oceanography 65:325–333, https://doi.org/10.1007/s10872-009-0030-z.

Kim, Y.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.

Li, R., Y.J. Kaufman, B. Gao, and C.O. Davis. 2003. Remote sensing of suspended sediments and shallow coastal waters. IEEE Transactions on Geoscience and Remote Sensing 41(3):559–566.

Liu, K.K., S.Y. Chao, P.T. Shaw, G.C. Gong, C.C. Chan, and T.Y. Tang. 2002. Monsoon-forced chlorophyll distribution and primary production in the South China Sea: Observations and a numerical study. Deep Sea Research Part 1 49:1,387–1,412, https://doi.org/10.1016/S0967-0637(02)00035-3

Lyman, J.M., and G.C. Johnson. 2008. Estimating annual global upper-ocean heat content anomalies despite irregular in situ ocean sampling. Journal of Climate 21(21):5,629–5,641, https://doi.org/10.1175/2008JCLI2259.1

McGillicuddy, D.J., A.R. Robinson, D.A. Siegel, H.W. Jannasch, R. Johnson, T.D. Dickey, J. McNeil, A.F. Michaels, and A.H. Knap. 1998. Influence of mesoscale eddies on new production in the Sargasso Sea. Nature 394:263–266, https://doi.org/10.1038/28367.

Mizobata, K., S.I. Saitoh, A. Shiomoto, T. Miyamura, N. Shiga, K. Imai, M. Toratani, Y. Kajiwara, and K. Sasaoka. 2002. Bering Sea cyclonic and anticyclonic eddies observed during summer 2000 and 2001. Progress in Oceanography 55:65–75, https://doi.org/10.1016/S0079-6611(02)00070-8.

Morel, A., and J.-F. Berthon. 1989. Surface pigments, algal biomass profiles, and potential production of the euphotic layer: Relationships reinvestigated in view of remote-sensing applications. Limnology and Oceanography 34(8):1,545–1,562, https://doi.org/10.4319/lo.1989.34.8.1545.

Morel, A., H. Claustre, and B. Gentili. 2010. The most oligotrophic subtropical zones of the global ocean: Similarities and differences in terms of chlorophyll and yellow substance. Biogeosciences 7:3,139–3,151, https://doi.org/​10.5194/bg-7-3139-2010

Qiu, B., and S. Chen. 2010a. Interannual-to-decadal variability in the bifurcation of the North Equatorial Current off the Philippines. Journal of Physical Oceanography 40(11):2,525–2,538, https://doi.org/10.1175/2010JPO4462.1

Qiu, B., and S. Chen. 2010b. Interannual variability of the North Pacific Subtropical Countercurrent and its associated mesoscale eddy field. Journal of Physical Oceanography 40:213–225, https://doi.org/10.1175/2009JPO4285.1.

Qiu, B., and S. Chen. 2012. Multidecadal sea level and gyre circulation variability in the northwestern tropical Pacific Ocean. Journal of Physical Oceanography 42(1):193–206, https://doi.org/​10.1175/JPO-D-11-061.1.

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.

Shiozaki, T., T. Kodama, S. Kitajima, M. Sato, and K. Furuya. 2013. Advective transport of diazotrophs and importance of their nitrogen fixation on new and primary production in the western Pacific warm pool. Limnology and Oceanography 58(1):49–60, https://doi.org/10.4319/lo.2013.58.1.0049.

Talley, L.D., G.L. Pickard, W.J. Emery, and J.H. Swift. 2011. Descriptive Physical Oceanography, 6th ed. Academic Press, Boston, 560 pp.

Uitz, J., H. Claustre, A. Morel, and S.B. Hooker. 2006. Vertical distribution of phytoplankton communities in open ocean: An assessment based on surface chlorophyll. Journal of Geophysical Research 111, C08005, https://doi.org/10.1029/2005JC003207.

Wang, Q.Y. 2006. Bifurcation of the North Equatorial Current derived from altimetry in the Pacific Ocean. Journal of Hydrodynamics 18(5):620–626, https://doi.org/10.1016/S1001-6058(06)60144-3.

Willis, J.K., D. Roemmich, and B. Cornuelle. 2004. Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales. Journal of Geophysical Research 109, C12036, https://doi.org/10.1029/2003JC002260

Xie, L., J. Tian, D. Hu, and F. Wang. 2009. A quasi-​synoptic interpretation of water mass distribution and circulation in the western North Pacific II: Circulation. Chinese Journal of Oceanology and Limnology 27(4):955–965, https://doi.org/10.1007/s00343-009-9240-x.