Editorial Type:
Article
Article Type:
Research Article

Effect of Mesoscale Eddies on Subtropical Mode Water Variability from the Kuroshio Extension System Study (KESS)

Bo Qiu Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii

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Shuiming Chen Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii

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Peter Hacker Department of Oceanography, University of Hawaii at Manoa, Honolulu, Hawaii

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Print Publication:
01 Apr 2007
DOI:
https://doi.org/10.1175/JPO3097.1
Page(s):
982–1000
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Abstract

Forty-eight profiling floats have been deployed in the Kuroshio Extension (KE) region since May 2004 as part of the Kuroshio Extension System Study (KESS) project. By combining the float temperature–salinity measurements with satellite altimetry data, this study investigates the role played by mesoscale eddies in controlling the property changes in North Pacific Subtropical Mode Water (STMW). Following a 3-yr period of low eddy activity in 2002–04, the KE showed a transition to a high eddy kinetic energy state in 2005. This transition is the result of delayed oceanic response to the 2002 shift in the basin-scale surface wind forcing in connection with the Pacific decadal oscillation. The high eddy kinetic energy state of the KE is characterized by successive shedding of strong cold-core rings into the recirculation gyre, resulting from the interaction of the KE jet with the Shatsky Rise or the preexisting cutoff rings. By transporting northern-origin, high-potential-vorticity (PV) KE water into the recirculation gyre, the enhanced eddy activity affects STMW in two ways: first, it hinders the formation of deep winter mixed layer (hence the source for STMW) by modifying the upper-ocean stratification and, second, it provides a direct high-PV source to mix with the surrounding low-PV STMW. The eddies’ influence upon STMW is observed to be both significant in magnitude and efficient in time. Relative to 2004, the PV signal in the core of STMW was reduced by one-half in 2005, and this weakening of STMW’s intensity occurred within a period of less than 7 months. This result supports recent findings by the authors based on historical temperature data that the variability in STMW formation depends more sensitively on the dynamic state of the KE than on the overlying atmospheric conditions.

Corresponding author address: Dr. Bo Qiu, Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI 96822. Email: bo@soest.hawaii.edu

Abstract

Forty-eight profiling floats have been deployed in the Kuroshio Extension (KE) region since May 2004 as part of the Kuroshio Extension System Study (KESS) project. By combining the float temperature–salinity measurements with satellite altimetry data, this study investigates the role played by mesoscale eddies in controlling the property changes in North Pacific Subtropical Mode Water (STMW). Following a 3-yr period of low eddy activity in 2002–04, the KE showed a transition to a high eddy kinetic energy state in 2005. This transition is the result of delayed oceanic response to the 2002 shift in the basin-scale surface wind forcing in connection with the Pacific decadal oscillation. The high eddy kinetic energy state of the KE is characterized by successive shedding of strong cold-core rings into the recirculation gyre, resulting from the interaction of the KE jet with the Shatsky Rise or the preexisting cutoff rings. By transporting northern-origin, high-potential-vorticity (PV) KE water into the recirculation gyre, the enhanced eddy activity affects STMW in two ways: first, it hinders the formation of deep winter mixed layer (hence the source for STMW) by modifying the upper-ocean stratification and, second, it provides a direct high-PV source to mix with the surrounding low-PV STMW. The eddies’ influence upon STMW is observed to be both significant in magnitude and efficient in time. Relative to 2004, the PV signal in the core of STMW was reduced by one-half in 2005, and this weakening of STMW’s intensity occurred within a period of less than 7 months. This result supports recent findings by the authors based on historical temperature data that the variability in STMW formation depends more sensitively on the dynamic state of the KE than on the overlying atmospheric conditions.

Corresponding author address: Dr. Bo Qiu, Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI 96822. Email: bo@soest.hawaii.edu

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  • Bingham, F. M., 1992: Formation and spreading of Subtropical Mode Water in the North Pacific. J. Geophys. Res., 97 , 11177–11189.

  • Bingham, F. M., T. Suga, and K. Hanawa, 1992: Comparison of upper ocean thermal conditions in the western North Pacific between two pentads: 1938–42 and 1978–82. J. Oceanogr., 48 , 405–425.

    • Search Google Scholar
    • Export Citation

  • Conkright, M. E., R. A. Locarnini, H. E. Garcia, T. D. O’Brien, T. P. Boyer, C. Stephens, and J. I. Antonov, 2002: World Ocean Atlas 2001: Objective analyses, data statistics, and figures. CD-ROM documentation. National Oceanographic Data Center, 17 pp.

  • Deser, C., M. A. Alexander, and M. S. Timlin, 2003: Understanding the persistence of sea surface temperature anomalies in midlatitude. J. Climate, 16 , 57–72.

    • Search Google Scholar
    • Export Citation

  • Dong, S., S. L. Hautala, and K. A. Kelly, 2007: Interannual variations in upper ocean heat content and heat transport convergence in the western North Atlantic. J. Phys. Oceanogr., in press.

    • Search Google Scholar
    • Export Citation

  • Ducet, N., P-Y. Le Traon, and G. Reverdin, 2000: Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2. J. Geophys. Res., 105 , 19477–19498.

    • Search Google Scholar
    • Export Citation

  • Ebuchi, N., and K. Hanawa, 2001: Trajectory of mesoscale eddies in the Kuroshio recirculation region. J. Oceanogr., 57 , 471–480.

  • Ferreira, D., J. Marshall, and P. Heimbach, 2005: Estimating eddy stresses by fitting dynamics to observations using a residual-mean ocean circulation model and its adjoint. J. Phys. Oceanogr., 35 , 1891–1910.

    • Search Google Scholar
    • Export Citation

  • Hanawa, K., and J. Kamada, 2001: Variability of core layer temperature (CLT) of the North Pacific subtropical mode water. Geophys. Res. Lett., 28 , 2229–2232.

    • Search Google Scholar
    • Export Citation

  • Hanawa, K., and L. D. Talley, 2001: Mode waters. Ocean Circulation and Climate: Observing and Modelling the Global Ocean, G. Siedler, J. Church, and J. Gould, Eds., Academic Press, 373–386.

    • Search Google Scholar
    • Export Citation

  • Hurlburt, H. E., A. J. Wallcraft, W. J. Schmitz, P. J. Hogan, and E. J. Metzger, 1996: Dynamics of the Kuroshio/Oyashio current system using eddy-resolving models of the North Pacific Ocean. J. Geophys. Res., 101 , 941–976.

    • Search Google Scholar
    • Export Citation

  • Kelly, K. A., 2004: The relationship between oceanic heat transport and surface fluxes in the western North Pacific: 1970–2000. J. Climate, 17 , 573–588.

    • Search Google Scholar
    • Export Citation

  • Kelly, K. A., and S. Dong, 2004: The relationship of western boundary current heat transport and storage to mid-latitude ocean–atmosphere interaction. Earth’s Climate: The Ocean-Atmosphere Interaction, Geophys. Monogr., Vol. 147, Amer. Geophys. Union, 347–363.

    • Search Google Scholar
    • Export Citation

  • Kistler, R., and Coauthors, 2001: The NCEP-NCAR 50-Year Reanalysis: Monthly means CD-ROM and documentation. Bull. Amer. Meteor. Soc., 82 , 247–267.

    • Search Google Scholar
    • Export Citation

  • Le Traon, P-Y., and G. Dibarboure, 1999: Mesoscale mapping capabilities of multiple-satellite altimeter missions. J. Atmos. Oceanic Technol., 16 , 1208–1223.

    • Search Google Scholar
    • Export Citation

  • Mantua, N. J., S. R. Hare, Y. Zhang, J. M. Wallace, and R. C. Francis, 1997: A Pacific interdecadal climate oscillation with impacts on salmon production. Bull. Amer. Meteor. Soc., 78 , 1069–1079.

    • Search Google Scholar
    • Export Citation

  • Masuzawa, J., 1969: Subtropical mode water. Deep-Sea Res., 16 , 463–472.

  • Masuzawa, J., 1972: Water characteristics of the North Pacific central region. Kuroshio—Its Physical Aspects, H. Stommel and K. Yoshida, Eds., University of Tokyo Press, 95–127.

    • Search Google Scholar
    • Export Citation

  • Mizuno, K., and W. B. White, 1983: Annual and interannual variability in the Kuroshio Current system. J. Phys. Oceanogr., 13 , 1847–1867.

    • Search Google Scholar
    • Export Citation

  • Oka, E., and T. Suga, 2003: Formation region of North Pacific subtropical mode water in the late winter of 2003. Geophys. Res. Lett., 30 .2205, doi:10.1029/2003GL018581.

    • Search Google Scholar
    • Export Citation

  • Qiu, B., 2002: The Kuroshio Extension system: Its large-scale variability and role in the midlatitude ocean–atmosphere interaction. J. Oceanogr., 58 , 57–75.

    • Search Google Scholar
    • Export Citation

  • Qiu, B., 2003: Kuroshio Extension variability and forcing of the Pacific decadal oscillations: Responses and potential feedback. J. Phys. Oceanogr., 33 , 2465–2482.

    • Search Google Scholar
    • Export Citation

  • Qiu, B., and S. Chen, 2005: Variability of the Kuroshio Extension jet, recirculation gyre and mesoscale eddies on decadal timescales. J. Phys. Oceanogr., 35 , 2090–2103.

    • Search Google Scholar
    • Export Citation

  • Qiu, B., and S. Chen, 2006: Decadal variability in the formation of the North Pacific Subtropical Mode Water: Oceanic versus atmospheric control. J. Phys. Oceanogr., 36 , 1365–1380.

    • Search Google Scholar
    • Export Citation

  • Qiu, B., P. Hacker, S. Chen, K. A. Donohue, D. R. Watts, H. Mitsudera, N. G. Hogg, and S. R. Jayne, 2006: Observations of the Subtropical Mode Water evolution from the Kuroshio Extension System Study. J. Phys. Oceanogr., 36 , 457–473.

    • Search Google Scholar
    • Export Citation

  • Stammer, D., 1998: On eddy characteristics, eddy transports, and mean flow properties. J. Phys. Oceanogr., 28 , 727–739.

  • Suga, T., and K. Hanawa, 1995a: The Subtropical Mode Water circulation in the North Pacific. J. Phys. Oceanogr., 25 , 958–970.

  • Suga, T., and K. Hanawa, 1995b: Interannual variations of North Pacific Subtropical Mode Water in the 137°E section. J. Phys. Oceanogr., 25 , 1012–1017.

    • Search Google Scholar
    • Export Citation

  • Suga, T., K. Motoki, Y. Aoki, and A. M. MacDonald, 2004: The North Pacific climatology of winter mixed layer and mode waters. J. Phys. Oceanogr., 34 , 3–22.

    • Search Google Scholar
    • Export Citation

  • Talley, L. D., 1988: Potential vorticity distribution in the North Pacific. J. Phys. Oceanogr., 18 , 89–106.

  • Taneda, T., T. Suga, and K. Hanawa, 2000: Subtropical mode water variation in the southwestern part of the North Pacific subtropical gyre. J. Geophys. Res., 105 , 19591–19598.

    • Search Google Scholar
    • Export Citation

  • Teague, W. J., M. J. Carron, and P. J. Hogan, 1990: A comparison between the Generalized Digital Environmental Model and Levitus climatologies. J. Geophys. Res., 95 , 7167–7183.

    • Search Google Scholar
    • Export Citation

  • Uehara, H., T. Suga, K. Hanawa, and N. Shikama, 2003: A role of eddies in formation and transport of North Pacific Subtropical Mode Water. Geophys. Res. Lett., 30 .1705, doi:10.1029/2003GL017542.

    • Search Google Scholar
    • Export Citation

  • Vivier, F., K. A. Kelly, and L. Thompson, 2002: Heat budget in the Kuroshio Extension region: 1993–1999. J. Phys. Oceanogr., 32 , 3436–3454.

    • Search Google Scholar
    • Export Citation

  • Wong, A., G. C. Johnson, and W. B. Owens, 2003: Delayed-mode calibration of autonomous CTD profiling float salinity data by θ–S climatology. J. Atmos. Oceanic Technol., 20 , 308–318.

    • Search Google Scholar
    • Export Citation

  • Wyrtki, K., L. Maygaad, and J. Hager, 1976: Eddy energy in the oceans. J. Geophys. Res., 81 , 2641–2646.

  • Yasuda, T., and K. Hanawa, 1999: Composite analysis of North Pacific subtropical mode water properties with respect to the strength of the wintertime East Asian monsoon. J. Oceanogr., 55 , 531–541.

    • Search Google Scholar
    • Export Citation
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