Article Type:
Research Article

On the Loss of Wind-Induced Near-Inertial Energy to Turbulent Mixing in the Upper Ocean

Xiaoming Zhai IFM-GEOMAR, Kiel, Germany

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Richard J. Greatbatch IFM-GEOMAR, Kiel, Germany

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Carsten Eden IFM-GEOMAR, Kiel, Germany

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Toshiyuki Hibiya Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Tokyo, Japan

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Print Publication:
01 Nov 2009
DOI:
https://doi.org/10.1175/2009JPO4259.1
Page(s):
3040–3045
Restricted access

Abstract

Wind-induced near-inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation. In the present study, the near-inertial energy budget in a realistic model of the North Atlantic Ocean driven by synoptically varying wind forcing is examined. The authors find that nearly 70% of the wind-induced near-inertial energy at the sea surface is lost to turbulent mixing within the top 200 m and, hence, is not available to generate diapycnal mixing at greater depth. Assuming this result can be extended to the global ocean, it is estimated that the wind-induced near-inertial energy available for ocean mixing at depth is, at most, 0.1 TW. This confirms a recent suggestion that the role of wind-induced near-inertial energy in sustaining the global overturning circulation might have been overemphasized.

* Current affiliation: University of Oxford, Oxford, United Kingdom.

Corresponding author address: Xiaoming Zhai, Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom. Email: zhai@atm.ox.ac.uk

Abstract

Wind-induced near-inertial energy has been believed to be an important source for generating the ocean mixing required to maintain the global meridional overturning circulation. In the present study, the near-inertial energy budget in a realistic model of the North Atlantic Ocean driven by synoptically varying wind forcing is examined. The authors find that nearly 70% of the wind-induced near-inertial energy at the sea surface is lost to turbulent mixing within the top 200 m and, hence, is not available to generate diapycnal mixing at greater depth. Assuming this result can be extended to the global ocean, it is estimated that the wind-induced near-inertial energy available for ocean mixing at depth is, at most, 0.1 TW. This confirms a recent suggestion that the role of wind-induced near-inertial energy in sustaining the global overturning circulation might have been overemphasized.

* Current affiliation: University of Oxford, Oxford, United Kingdom.

Corresponding author address: Xiaoming Zhai, Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom. Email: zhai@atm.ox.ac.uk

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