Acta Oceanologica Sinica

, Volume 36, Issue 5, pp 26–30 | Cite as

The variation of turbulent diapycnal mixing at 18°N in the South China Sea stirred by wind stress

Article

Abstract

The spatial and temporal variations of turbulent diapycnal mixing along 18°N in the South China Sea (SCS) are estimated by a fine-scale parameterization method based on strain, which is obtained from CTD measurements in yearly September from 2004 to 2010. The section mean diffusivity can reach ~10–4 m2/s, which is an order of magnitude larger than the value in the open ocean. Both internal tides and wind-generated near-inertial internal waves play an important role in furnishing the diapycnal mixing here. The former dominates the diapycnal mixing in the deep ocean and makes nonnegligible contribution in the upper ocean, leading to enhanced diapycnal mixing throughout the water column over rough topography. In contrast, the influence of the wind-induced near-inertial internal wave is mainly confined to the upper ocean. Over both flat and rough bathymetries, the diapycnal diffusivity has a growth trend from 2005 to 2010 in the upper 700 m, which results from the increase of wind work on the near-inertial motions.

Key words

diapycnal mixing diffusivity wind-induced near-inertial internal wave topography 

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Notes

Acknowledgements

The authors thank the Key Laboratory of Tropical Marine Environment Dynamics, the South China Sea Institute of Oceanology, Chinese Academy of Sciences for providing the CTD data. We are grateful for the suggestions from Yang Qingxuan.

References

  1. Alford M. 2001. Internal swell generation: the spatial distribution of energy flux from the wind to mixed layer near-inertial motions. J Phys Oceanogr, 31(8): 2359–2368CrossRefGoogle Scholar
  2. Alford M H. 2003. Improved global maps and 54-year history of windwork on ocean inertial motions. Geophys Res Lett, 30(8): 1424CrossRefGoogle Scholar
  3. Alford M H, Peacock T, MacKinnon J A, et al. 2015. The formation and fate of internal waves in the South China Sea. Nature, 521(7550): 65–69CrossRefGoogle Scholar
  4. Egbert G D, Ray R D. 2001. Estimates of M2 tidal energy dissipation from TOPEX/Poseidon altimeter data. J Geophys Res, 106(C10): 22475–22502CrossRefGoogle Scholar
  5. Ge Lili, Cheng Xuhua, Qi Yiquan, et al. 2012. Upper-layer geostrophic volume, heat and salt transports across 18°N in the South China Sea. J Trop Oceanogr (in Chinese), 31(1): 10–17Google Scholar
  6. Gill A E, Green J S A, Simmons A J. 1974. Energy partition in the largescale ocean circulation and the production of mid-ocean eddies. Deep-Sea Res: Oceanogr Abstr, 21(7): 499–528Google Scholar
  7. Gregg M C. 1987. Diapycnal mixing in the thermocline: a review. J Geophys Res, 92(C5): 5249–5289CrossRefGoogle Scholar
  8. Gregg M C, Kunze E. 1991. Internal wave shear and strain in Santa Monica basin. J Geophys Res, 96(C9): 16709–16719CrossRefGoogle Scholar
  9. Gregg M C, Sanford T B, Winkel D P. 2003. Reduced mixing from the breaking of internal waves in equatorial ocean waters. Nature, 422(6931): 513–515CrossRefGoogle Scholar
  10. Jayne S R, St Laurent L C. 2001. Parameterizing tidal dissipation over rough topography. Geophys Res Lett, 28(5): 811–814CrossRefGoogle Scholar
  11. Jing Zhao, Wu Lixin. 2010. Seasonal variation of turbulent diapycnal mixing in the northwestern pacific stirred by wind stress. Geophys Res Lett, 37(23): L23604CrossRefGoogle Scholar
  12. Jing Zhao, Wu Lixin. 2014. Intensified diapycnal mixing in the midlatitude western boundary currents. Sci Rep, 4: 7412CrossRefGoogle Scholar
  13. Jing Zhao, Wu Lixin, Li Lei, et al. 2011. Turbulent diapycnal mixing in the subtropical northwestern pacific: spatial-seasonal variations and role of eddies. J Geophys Res, 116(C10): C10028CrossRefGoogle Scholar
  14. Kunze E, Firing E, Hummon J M, et al. 2006. Global abyssal mixing inferred from lowered ADCP shear and CTD strain profiles. J Phys Oceanogr, 36(8): 1553–1576CrossRefGoogle Scholar
  15. Kunze E, Kennelly M A, Sanford T B. 1992. The depth dependence of shear finestructure off Point Arena and near Pioneer Seamount. J Phys Oceanogr, 22(1): 29–41Google Scholar
  16. Li Ying, Xu Yongsheng. 2014. Penetration depth of diapycnal mixing generated by wind stress and flow over topography in the northwestern pacific. J Geophys Res, 119(8): 5501–5514CrossRefGoogle Scholar
  17. Munk W, Wunsch C. 1998. Abyssal recipes: II. Energetics of tidal and wind mixing. Deep-Sea Res: I, 45(12): 1977–2010Google Scholar
  18. Pollard R T, Millard R C. 1970. Comparison between observed and simulated wind-generated inertial oscillations. Deep-Sea Res: Oceanogr Abstr, 17(4): 813–816Google Scholar
  19. Polzin K L, Toole J M, Schmitt R W. 1995. Finescale parameterizations of turbulent dissipation. J Phys Oceanogr, 25(3): 306–328CrossRefGoogle Scholar
  20. Tian Jiwei, Yang Qingxuan, Zhao Wei. 2009. Enhanced diapycnal mixing in the South China Sea. J Phys Oceanogr, 39(12): 3191–3203CrossRefGoogle Scholar
  21. Waterhouse A F, Mackinnon J A, Nash J D, et al. 2014. Global patterns of diapycnal mixing from measurements of the turbulent dissipation rate. J Phys Oceanogr, 44(7): 1854–1872CrossRefGoogle Scholar
  22. Whalen C B, Talley L D, MacKinnon J A. 2012. Spatial and temporal variability of global ocean mixing inferred from Argo profiles. Geophys Res Lett, 39(18): L18612CrossRefGoogle Scholar
  23. Wu Lixin, Jing Zhao, Riser S, et al. 2011. Seasonal and spatial variations of Southern Ocean diapycnal mixing from Argo profiling floats. Nat Geosci, 4(6): 363–366CrossRefGoogle Scholar
  24. Wunsch C, Ferrari R. 2004. Vertical mixing, energy, and the general circulation of the oceans. Annu Rev Fluid Mech, 36(1): 281–314CrossRefGoogle Scholar
  25. Yang Haiyuan, Wu Lixin. 2012. Trends of upper-layer circulation in the South China Sea during 1959–2008. J Geophys Res, 117(C8): C08037CrossRefGoogle Scholar
  26. Zhai Xiaoming, Greatbatch R J, Eden C, et al. 2009. On the loss of wind-induced near-inertial energy to turbulent mixing in the upper ocean. J Phys Oceanogr, 39(11): 3040–3045CrossRefGoogle Scholar

Copyright information

© The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Physical Oceanography LaboratoryOcean University of China/CIMSTQingdaoChina
  2. 2.Qingdao National Laboratory for Marine Science and TechnologyQingdaoChina
  3. 3.Department of OceanographyTexas A&M UniversityCollege StationUSA

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