Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 16 6 2009 10.5194/npg-16-665-2009 http://www.nonlin-processes-geophys.net/16/665/2009/ http://www.nonlin-processes-geophys.net/16/665/2009/npg-16-665-2009.html http://www.nonlin-processes-geophys.net/16/665/2009/npg-16-665-2009.pdf 665 675 2009-12-14 Low-frequency variability of the Kuroshio Extension S. Pierini H. A. Dijkstra dijkstra@phys.uu.nl Dipartimento di Scienze per l'Ambiente, Università di Napoli Parthenope, Naples, Italy Institute for Marine and Atmospheric research Utrecht, Department of Physics and Astronomy, Utrecht University, Utrecht, The Netherlands In this paper, we provide a review of recent results targeted at the understanding of the low-frequency variability of the Kuroshio Extension. We provide the background and main arguments of two views which have recently been proposed to explain this variability. In the first view, wind-induced Rossby waves and the effects of mesocale eddies are crucial. The second view is based on low-dimensional equivalent-barotropic large-scale nonlinear dynamics, with neither Rossby wave dynamics nor baroclinic instability being important. Results from models supporting each view are discussed and confronted with results from available observations. Cessi, P. and Ierley, G R.: Symmetry-breaking multiple equilibria in quasi-geostrophic, wind-driven flows, J. Phys. Oceanogr., 25, 1196–1205, 1995. Chang, K.-I., Ghil, M., Ide, K., and Lai, C.-C A.: Transition to aperiodic variability in a wind-driven double-gyre circulation model, J. Phys.\ Oceanogr., 31, 1260–1286, 2001. Dijkstra, H A.: Nonlinear Physical Oceanography: A Dynamical Systems Approach to the Large Scale Ocean Circulation and El Niño., Kluwer Academic Publishers, Dordrecht, The Netherlands, 2000. Dijkstra, H A. and De~Ruijter, W. P M.: Finite Amplitude Stability of the Wind-Driven Ocean Circulation, Geophys. Astrophys. Fluid, 83, 1–31, 1996. Dijkstra, H A. and Katsman, C A.: Temporal variability of the Wind-Driven Quasi-geostrophic Double Gyre Ocean Circulation: Basic Bifurcation Diagrams, Geophys. Astrophys. Fluid, 85, 195–232, 1997. Donohue, K., Watts, D. R., Tracey, K., Wimbush, M., and Park, J.: Program Studies the Kuroshio Extension, EOS T. Am. Geophys. Un., 89, 161–162, 2008. Jiang, S., Jin, F.-F., and Ghil, M.: Multiple equilibria and aperiodic solutions in a wind-driven double-gyre, shallow-water model, J. Phys.\ Oceanogr., 25, 764–786, 1995. Mantua, N J., Hare, S., Zhang, Y., Wallace, J M., and Francis, R C.: A Pacific interdecadal climate oscillation with impacts on salmon production, B. Am. Meteorol. Soc., 78, 1069–1079, 1997. McCalpin, J D. and Haidvogel, D B.: Phenomenology of the low-frequency variabiliity in a reduced gravity quasi-geostrophic double-gyre model, J.\ Phys. Oceanogr., 26, 739–752, 1996. Meacham, S P.: Low frequency variability of the wind-driven circulation, J.\ Phys. Oceanogr., 30, 269–293, 2000. Munk, W.: On the wind-driven ocean circulation, J. Meteorol., 7, 79–93, 1950. Nadiga, B T. and Luce, B.: Global bifurcation of Shilñikov type in a double-gyre model, J. Phys. Oceanogr., 31, 2669–2690, 2001. Nauw, J., Dijkstra, H A., and Simonnet, E.: Regimes of low-frequency variability in a three-layer quasi-geostrophic model, J. Mar. Res., in press, 2004. Pedlosky, J.: Geophysical Fluid Dynamics, 2nd edn., Springer-Verlag, New York, 1987. Pierini, S.: A Kuroshio Extension system model study: decadal chaotic self-sustained oscillations, J. Phys. Oceanogr., 36, 1605–1620, 2006. Pierini, S.: On the crucial role of basin geometry in double-gyre models of the Kuroshio Extension, J. Phys. Oceanogr., 38, 1327–1333, 2008. Pierini, S.: Coherence resonance in a double-gyre model of the Kuroshio Extension, J. Phys. Oceanogr., in press, 2009. Pierini, S., Dijkstra, H A., and Riccio, A.: A nonlinear theory of the Kuroshio Extension Bimodality, J. Phys. Oceanogr., 39, 2212–2229, 2009. Primeau, F W.: Multiple equilibria and low-frequency variability of the wind-driven ocean circulation, J. Phys. Oceanogr., 32, 2236–2256, 2002. Qiu, B.: Interannual variability of the Kuroshio Extension System and its impact on the wintertime SST field , J. Phys. Oceanogr., 30, 1486–1502, 2000. Qiu, B. and Chen, S.: Variability of the Kuroshio Extension Jet, Recirculation Gyre and Mesocale Eddies on decadal time scales, J. Phys.\ Oceanogr., 35, 2090–2103, 2005. Qiu, B. and Chen, S.: Eddy-Mean flow interaction in the decadallly modulating Kuroshio Extension system, Deep-Sea Res., in press, 2009. Qiu, B. and Miao, W.: Kuroshio Extension variability and forcing of the Pacific Decadal Oscillations: responses and potential feedback, J. Phys.\ Oceanogr., 33, 2465–2482, 2000. Qiu, B., Hacker, P., Chen, S., Donohue, K A., Randolph~Watts, D., Mitsudera, H., Hogg, N G., and Jayne, S R.: Observations of the subtropical mode water evolution from the Kuroshio Extension System Study, J. Phys.\ Oceanogr., 36, 457–473, 2006. Schmeits, M J. and Dijkstra, H A.: Bimodality of the Kuroshio and the Gulf Stream, J. Phys. Oceanogr., 31, 2971–2985, 2001. Simonnet, E. and Dijkstra, H A.: Spontaneous generation of low-frequency modes of variability in the wind-driven ocean circulation, J. Phys.\ Oceanogr., 32, 1747–1762, 2002. Simonnet, E., Dijkstra, H A., and Ghil, M.: Homoclinic bifurcations in the quasi-geostrophic double-gyre circulation, J. Mar. Res., 63, 931–956, 2005. Speich, S., Dijkstra, H., and Ghil, M.: Successive bifurcations in a shallow-water model applied to the wind-driven ocean circulation, Nonlin. Processes Geophys., 2, 241–268, 1995. Stommel, H.: The westward intensification of wind-driven ocean currents, EOS T. Am. Geophys. Un., 29, 202–206, 1948. Sverdrup, H U.: Wind-driven currents in a baroclinic ocean with application to the equatorial current in the eastern Pacific, P. Natl. Acad. Sci. USA, Wash., 33, 318–326, 1947. Taft, B A.: Characteristics of the flow of the Kuroshio south of Japan, in: Kuroshio, physical aspects of the Japan current, edited by: Stommel, H. and Yoshida, K., Univ. Washington Press, Seattle, USA, 1972. Taguchi, B., Xie, S.-P., Mitsudera, H., and Kubokawa, A.: Response of the Kuroshio Extension to Rossby waves associated with the 1970s climate shift in a high resolution ocean model, J. Climate, 18, 2979–2995, 2005. Taguchi, B., Xie, S.-P., Schneider, N., Nonaka, M., Sasaki, H., and Sasai, Y.: Decadal variability of the Kuroshio Extension: Observations and an eddy-resolving model hincast, J. Climate, 20, 2357–2377, 2007. Teague, W J., Carron, M J., and Hogan, P J.: A comparison between the generalized digital environment model and Levitus climatologies, J.\ Geophys. Res., 95, 7167–7183, 1990. Veronis, G.: An analysis of the wind-driven ocean circulation with a limited number of Fourier components, J. Atmos. Sci., 20, 577–593, 1963. Wiggins, S.: Introduction to Applied Nonlinear Dynamical Systems and Chaos, Springer-Verlag, Heidelberg-Berlin, Germany, 1990.