Abstract
The mixing processes in the Mixed Water Region (MWR) that lead to changes in the properties of North Pacific Intermediate Water (NPIW) have been studied using observational data sets obtained in May–June 1998. Neutral surfaces, the equation of water mass conversion rate on neutral surfaces and the equation of vertical velocity across neutral surfaces have been used to distinguish dominant processes by assuming the horizontal scale to be the streamer scale (under 100 km). The possibility of double diffusive convection is also discussed in relation to the density ratio. These results may be summarized as follows: (1) the difference between the potential density surface and the neutral surface may rise to −0.04 kg/m3 around the source water of NPIW; (2) horizontal diffusion causes strong modifications of the source water of NPIW; (3) the density range within which strong modification of the source water of NPIW occurs becomes dense from the northern part of MWR near the Oyashio Front to the southern part near the Kuroshio Front, and to the eastern part. Our modeling of these processes shows that cabbeling has effects on the density increment of the source water of NPIW in the northern and southern part of MWR. Double diffusive convection has effects on the density increment of the source water of NPIW, mainly in the northern part of MWR. The possible density increment due to cabbeling in these areas is estimated to be 0.01≈0.03 kg/m3. The possible density increment due to double diffusive convection is 0.01≈0.03 kg/m3. The total density increment due to cabbeling and double diffusive convection amounts to 0.06 kg/m3.
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References
Foster, T. D. (1972): An analysis of the Cabbeling instability in seawater. J. Phys. Oceanogr., 2, 294–301.
Gregg, M. C. (1989): Scaling turbulent dissipation in the thermocline. J. Geophys. Res., 94, 9686–9698.
Hebert, D. (1988): Estimates of salt-finger fluxes. Deep-Sea Res., 35, 1887–1901.
Jackett, D. R. and T. J. McDougall (1997): A neutral density variable for the world's oceans. J. Phys. Oceanogr., 27, 237–263.
Kelley, D. E. (1990): Fluxes through diffusive staircases. J. Geophys. Res., 95, 3365–3371.
McDougall, T. J. (1987a): Neutral surfaces. J. Phys. Oceanogr., 17, 1950–1964.
McDougall, T. J. (1987b): Thermobaricity, cabbeling, and water-mass conversion. J. Geophys. Res., 92, 5448–5464.
Miyake, H., S. Sakai, H. Yamaguchi, K. Masuda, G. Anma and Y. Kamei (1995): Thermohaline staircases in the warm-core ring off Cape Erimo, Hokkaido and their fluxes due to salt finger. J. Oceanogr., 51, 99–109.
Nagasaka, M., J. Yoshida, H. Nagashima, M. Matsuyama, K. Kawasaki and K. Yokouchi (1999): On the double diffusive intrusion observed in the Oyashio Frontal Region. Theoretical and Applied Mechanics, 48, 385–392.
Okubo, A. (1971): Oceanic diffusion diagrams. Deep-Sea Res., 18, 789–802.
Reid, J. L., Jr. (1965): Intermediate waters of the Pacific Ocean. The Johns Hopkins Oceanographic Studies, 2, 85 pp.
Schmitt, R. W. (1981): Form of the temperature-salinity relationship in the central water: Evidence for double-diffusive mixing. J. Phys. Oceanogr., 11, 1015–1026.
Schmitt, R. W. (1991): Overview of C-SALT. WHOI Tech. Report, WHOI-91-20, 11–30.
Schmitt, R. W. (1998): Double-diffusive convection: Its role in ocean mixing and parameterization schemes for large scale modeling. p. 215–234. In Ocean Modeling and Parameterization, ed. by E. Chassignet and J. Verron, Kluwer Academic Publishers.
Sverdrup, H. U., M. W. Johnson and R. H. Fleming (1942): The Oceans: Their Physics, Chemistry and General Biology. Prentice-Hall, Englewood Cliffs, New York, 1087 pp.
Talley, L. D. (1993): Distribution and formation of North Pacific Intermediate Water. J. Phys. Oceanogr., 23, 517–537.
Talley, L. D. and J. Y. Yun (2001): The role of cabbeling and double diffusion in setting the density of the North Pacific Intermediate Water salinity minimum. J. Phys. Oceanogr., 31, 1538–1549.
Talley, L. D., Y. Nagata, M. Fujimura, T. Iwao, T. Kono, D. Inagake, M. Hirai and K. Okuda (1995): North Pacific Intermediate Water in the Kuroshio/Oyashio Mixed Water Region. J. Phys. Oceanogr., 25, 475–501.
Yasuda, I. (1997): The origin of the North Pacific Intermediate Water. J. Geophys. Res., 102, 893–909.
Yasuda, I., K. Okuda and Y. Shimizu (1996): Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone. J. Phys. Oceanogr., 26, 448–465.
Yasuda, I., Y. Hiroe, K. Komatsu, K. Kawasaki, T. M. Joyce, F. Bahr and Y. Kawasaki (2001): Hydrographic structure and transport of the Oyashio south of Hokkaido and the formation of North Pacific Intermediate Water. J. Geophys. Res., 106, 6931–6942.
You, Y., N. Suginohara, M. Fukasawa, I. Yasuda, I. Kaneko, H. Yoritaka and M. Kawamiya (2000): Roles of the Okhotsk Sea and Alaskan Gyre in forming the North Pacific Intermediate Water. J. Geophys. Res., 105, 3253–3280.
Zhang, J., R. W. Schmitt and R. X. Huang (1998): Sensitivity of the GFDL modular ocean model to parameterization of double-diffusive process. J. Phys. Oceanogr., 28, 589–605.
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Inoue, R., Yoshida, J., Hiroe, Y. et al. Modification of North Pacific Intermediate Water around Mixed Water Region. Journal of Oceanography 59, 211–224 (2003). https://doi.org/10.1023/A:1025595322497
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DOI: https://doi.org/10.1023/A:1025595322497