Observations of the Subtropical Mode Water Evolution from the Kuroshio Extension System Study

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

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Kathleen A. Donohue Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island

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D. Randolph Watts Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island

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Humio Mitsudera Graduate School of Environmental Earth Science, University of Hokkaido, Sapporo, Japan

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Nelson G. Hogg Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

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Steven R. Jayne Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

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Abstract

Properties and seasonal evolution of North Pacific Ocean subtropical mode water (STMW) within and south of the Kuroshio Extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard ADCP measurements taken during 2004. The presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of STMW. Within the recirculation gyre, STMW formed from late-winter convection that reached depths greater than 450 m near the center of the gyre. The lower boundary of STMW, corresponding to σθ ≃ 25.5 kg m−3, was set by the maximum depth of the late-winter mixed layer. Properties within the deep portions of the STMW layer remained largely unchanged as the season progressed. In contrast, the upper boundary of the STMW layer eroded steadily as the seasonal thermocline deepened from late April to August. Vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of potential vorticity to be in the range of ∼2–5 × 10−4 m2 s−1. The latitudinal extent of the STMW formation was narrow, extending from 30°N to the Kuroshio Extension jet near 35°N. South of 30°N, STMW did not form locally but was transported from the recirculation gyre by lateral induction.

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

Properties and seasonal evolution of North Pacific Ocean subtropical mode water (STMW) within and south of the Kuroshio Extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard ADCP measurements taken during 2004. The presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of STMW. Within the recirculation gyre, STMW formed from late-winter convection that reached depths greater than 450 m near the center of the gyre. The lower boundary of STMW, corresponding to σθ ≃ 25.5 kg m−3, was set by the maximum depth of the late-winter mixed layer. Properties within the deep portions of the STMW layer remained largely unchanged as the season progressed. In contrast, the upper boundary of the STMW layer eroded steadily as the seasonal thermocline deepened from late April to August. Vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of potential vorticity to be in the range of ∼2–5 × 10−4 m2 s−1. The latitudinal extent of the STMW formation was narrow, extending from 30°N to the Kuroshio Extension jet near 35°N. South of 30°N, STMW did not form locally but was transported from the recirculation gyre by lateral induction.

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 , 1117711189.

  • Deser, C., M. A. Alexander, and M. S. Timlin, 1999: Evidence for a wind-driven intensification of the Kuroshio Current Extension from the 1970s to the 1980s. J. Climate, 12 , 16971706.

    • 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 , 1947719498.

    • Search Google Scholar
    • Export Citation
  • Gill, A. E., 1982: Atmosphere-Ocean Dynamics. Academic Press, 662 pp.

  • Gregg, M. C., and T. B. Sanford, 1980: Signatures of mixing from the Bermuda Slope, the Sargasso Sea and the Gulf Stream. J. Phys. Oceanogr, 10 , 105127.

    • Search Google Scholar
    • Export Citation
  • Hanawa, K., 1987: Interannual variations of the winter-time outcrop area of subtropical mode water in the western North Pacific Ocean. Atmos.–Ocean, 25 , 358374.

    • 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
  • Huang, R-X., and B. Qiu, 1994: Three-dimensional structure of the wind-driven circulation in the subtropical North Pacific. J. Phys. Oceanogr, 24 , 16081622.

    • Search Google Scholar
    • Export Citation
  • Jayne, S. R., N. G. Hogg, and P. Malanotte-Rizzoli, 1996: Recirculation gyres forced by a beta-plane jet. J. Phys. Oceanogr, 26 , 492504.

    • Search Google Scholar
    • Export Citation
  • Ledwell, J. R., A. J. Watson, and C. D. Law, 1993: Evidence for slow mixing across the pycnocline from an open-ocean tracer-release experiment. Nature, 364 , 701703.

    • 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 , 12081223.

    • Search Google Scholar
    • Export Citation
  • Masuzawa, J., 1969: Subtropical mode water. Deep-Sea Res, 16 , 463472.

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

    • Search Google Scholar
    • Export Citation
  • Miller, A. J., D. R. Cayan, and W. B. White, 1998: A westward-intensified decadal change in the North Pacific thermocline and gyre-scale circulation. J. Climate, 11 , 31123127.

    • 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 , 18471867.

    • 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., 2003: Kuroshio Extension variability and forcing of the Pacific decadal oscillations: Responses and potential feedback. J. Phys. Oceanogr, 33 , 24652482.

    • Search Google Scholar
    • Export Citation
  • Qiu, B., and K. A. Kelly, 1993: Upper ocean heat balance in the Kuroshio Extension region. J. Phys. Oceanogr, 23 , 20272041.

  • Qiu, B., and S. Chen, 2005: Variability of the Kuroshio Extension jet, recirculation gyre, and mesoscale eddies on decadal time scales. J. Phys. Oceanogr, 35 , 20902103.

    • 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, in press.

    • Search Google Scholar
    • Export Citation
  • Stommel, H. M., 1979: Determination of water mass properties of water pumped down from the Ekman layer to the geostrophic flow below. Proc. Nat. Acad. Sci. USA, 76 , 30513055.

    • Search Google Scholar
    • Export Citation
  • Suga, T., and K. Hanawa, 1995: The subtropical mode water circulation in the North Pacific. J. Phys. Oceanogr, 25 , 958970.

  • Suga, T., K. Hanawa, and Y. Toba, 1989: Subtropical mode water in the 137°E section. J. Phys. Oceanogr, 19 , 16051618.

  • Suga, T., Y. Taket, and K. Hanawa, 1997: Thermostad distribution in the North Pacific subtropical gyre: The central mode water and the subtropical mode water. J. Phys. Oceanogr, 27 , 140152.

    • Search Google Scholar
    • Export Citation
  • Talley, L. D., 1988: Potential vorticity distribution in the North Pacific. J. Phys. Oceanogr, 18 , 89106.

  • 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 , 71677183.

    • 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
  • Wentz, F. J., C. Gentemann, D. Smith, and D. Chelton, 2000: Satellite measurements of sea surface temperature through clouds. Science, 288 , 847850.

    • 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 θS climatology. J. Atmos. Oceanic Technol, 20 , 308318.

    • Search Google Scholar
    • Export Citation
  • Yasuda, T., and K. Hanawa, 1997: Decadal changes in the mode waters in the midlatitude North Pacific. J. Phys. Oceanogr, 27 , 858870.

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