Abstract
Two deep channels that cut through the Luzon Strait facilitate deep (>2000 m) water exchange between the western Pacific Ocean and the South China Sea. Our observations rule out the northern channel as a major exchange conduit. Rather, the southern channel funnels deep water from the western Pacific to the South China Sea at the rate of 1.06 ± 0.44 Sv (1 Sv = 106 m3s−1). The residence time estimated from the observed inflow from the southern channel, about 30 to 71 years, is comparable to previous estimates. The observation-based estimate of upwelling velocity at 2000 m depth is (1.10 ± 0.33) × 10−6 ms−1, which is of the same order as Ekman pumping plus upwelling induced by the geostrophic current. Historical hydrographic observations suggest that the deep inflow is primarily a mixture of the Circumpolar Deep Water and Pacific Subarctic Intermediate Water. The cold inflow through the southern channel offsets about 40% of the net surface heat gain over the South China Sea. Balancing vertical advection with vertical diffusion, the estimated mean vertical eddy diffusivity of heat is about 1.21 × 10−3 m2s−1. The cold water inflow from the southern channel maintains the shallow thermocline, which in turn could breed internal wave activities in the South China Sea.
Similar content being viewed by others
References
Alford, M. (2003): Redistribution of energy available for ocean mixing by long-range propagation of internal waves. Nature, 423, 159–162.
Chao, S.-Y., P. T. Shaw and S. Y. Wu (1996): Deep water ventilation in the South China Sea. Deep-Sea Res. I, 43, 445–466.
Chelton, D. B., R. A. deSzoeke, M. G. Schlax, K. El Naggar and N. Siwertz (1998): Geographical variability of the first-baroclinic Rossby radius of deformation. J. Phys. Oceanogr., 28, 433–460.
Chu, T. Y. (1972): A study of the water exchange between Pacific Ocean and the South China Sea. Acta Oceanogr. Taiwanica, 2, 11–24.
Duda, T. F., J. F. Lynch, J. D. Irish, R. C. Beardsley, S. R. Ramp, C.-S. Chiu, T. Y. Tang and Y. J. Yang (2004): Internal tide and nonlinear internal wave behavior at the continental slope in the northern South China Sea. IEEE J. Oceanic Eng., 29, 1105–1130.
Emery, W. J. (2001): Water types and water masses. p. 1556–1567. In Encyclopedia of Ocean Sciences, ed. by J. Steele, S. Thrope and K. Turekain, Academic Press, 3000 pp.
Gong, G.-C., K. K. Liu, C.-T. Liu and S.-C. Pai (1992): The chemical hydrography of the South China Sea west of Luzon and a comparison with the west Philippine Sea. Terres., Atmos. Ocean. Sci., 3(4), 587–602.
Kallberg, P., P. Berrisford, B. Hoskins, A. Simmons, S. Uppala, S. Lamy-Thepaut and R. Hine (2005): ERA-40 atlas. Technical report, ERA-40 Project Report Series, ECMWF, Shinfield Park, Reading, U.K., 191 pp.
Kunze, E., E. Firing, J. M. Hummon, T. K. Chereskin and A. M. Thurnherr (2006): Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. J. Phys. Oceanogr., 36, 1553–1576.
Lin, M.-Y. (2000): Numerical study of bottom circulation in the South China Sea. M.S. dissertation, National Taiwan University, Institute of Oceanography, 53 pp. (in Chinese).
Liu, C.-T. and R.-J. Liu (1988): The deep current in the Bashi Channel. Acta Oceanogr. Taiwanica, 20, 107–116.
Nitani, H. (1972): Beginning of the Kuroshio. p. 129–163. In Kuroshio: Its Physical Aspects of the Japan Current, ed. by H. Stommel and K. Yoshida, Univ. of Washington Press, Seattle, Washington, 517 pp.
Polzin, K. L., J. M. Toole, J. R. Ledwell and R. W. Schmitt (1997): Spatial variability of turbulent mixing in the abyssal ocean. Science, 276, 93–96.
Qu, T. (2000): Upper-layer circulation in the South China Sea. J. Phys. Oceanogr., 30, 1450–1460.
Qu, T., J. B. Girton and J. A. Whitehead (2006): Deepwater overflow through Luzon Strait. J. Geophys. Res., 111(C1), C01002, doi:10.1029/2005JC003139.
Qu, T., Y. T. Song and T. Yamagata (2009): An introsduction to the South China Sea Throughflow: Its dynamics, variability, and application for climate. Dyn. Atmos. Oceans, 47, 3–14.
Ramp, R. S., T. Y. Tang, T. F. Duda, J. F. Lynch, A. K. Liu, C.-S. Chiu, F. Bahr, H.-R. Kim and Y. J. Yang (2004): Internal solitons in the northeastern South China Sea Part I: Source and deep water propagation. IEEE J. Oceanic Eng., 29, 1157–1181.
Shaw, P.-T. and S.-Y. Chao (1994): Surface circulation in the South China Sea. Deep-Sea Res. I, 41, 1663–1683.
Stommel, H. (1958): The abyssal circulation. Deep-Sea Res., 5, 80–82.
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.
Toole, J. M., R. W. Schmitt and K. L. Polzin (1994): Estimates of diapycnal mixing in the abyssal ocean. Science, 264, 1120–1123.
Tozuka, T., T. Qu, Y. Masumoto and T. Yamagata (2009): Impacts of the South China Sea Throughflow on seasonal and interannual variations of the Indoneasian Throughflow. Dyn. Atmos. Oceans, 47, 73–85.
Wang, J. (1986): Observation of abyssal flows in the Northern South China Sea. Acta Oceanogr. Taiwanica, 16, 36–45.
Wyrtki, K. (1961): Physical oceanography of the Southeast Asian waters. Naga Rep. 2, 195 pp.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Chang, YT., Hsu, WL., Tai, JH. et al. Cold deep water in the South China Sea. J Oceanogr 66, 183–190 (2010). https://doi.org/10.1007/s10872-010-0016-x
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10872-010-0016-x