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Ocean Science An interactive open-access journal of the European Geosciences Union

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Ocean Sci., 12, 743-769, 2016
http://www.ocean-sci.net/12/743/2016/
doi:10.5194/os-12-743-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
01 Jun 2016
Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean
Julien Jouanno1,2, Xavier Capet2, Gurvan Madec2,3, Guillaume Roullet4, and Patrice Klein4 1LEGOS, Université de Toulouse, IRD, CNRS, CNES, UPS, Toulouse, France
2CNRS-IRD-Sorbonne Universités, UPMC, MNHN, LOCEAN Laboratory, Paris, France
3National Oceanographic Centre, Southampton, UK
4University of Brest, CNRS, IRD, Ifremer, Laboratoire d'Océanographie Physique et Spatiale (LOPS), IUEM, Brest, France
Abstract. The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized numerical model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean located between 70 and 40° S. It incorporates physical ingredients deemed essential for Southern Ocean functioning: rough topography, seasonally varying air–sea fluxes, and high-latitude storms with analytical form. The forcing strategy ensures that the time mean wind stress is the same between the different simulations, so the effect of the storms on the mean wind stress and resulting impacts on the Southern Ocean dynamics are not considered in this study. Level and distribution of mixing attributable to high-frequency winds are quantified and compared to those generated by eddy–topography interactions and dissipation of the balanced flow. Results suggest that (1) the synoptic atmospheric variability alone can generate the levels of mid-depth dissipation frequently observed in the Southern Ocean (10−10–10−9 W kg−1) and (2) the storms strengthen the overturning, primarily through enhanced mixing in the upper 300 m, whereas deeper mixing has a minor effect. The sensitivity of the results to horizontal resolution (20, 5, 2 and 1 km), vertical resolution and numerical choices is evaluated. Challenging issues concerning how numerical models are able to represent interior mixing forced by high-frequency winds are exposed and discussed, particularly in the context of the overturning circulation. Overall, submesoscale-permitting ocean modeling exhibits important delicacies owing to a lack of convergence of key components of its energetics even when reaching Δx =  1 km.

Citation: Jouanno, J., Capet, X., Madec, G., Roullet, G., and Klein, P.: Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean, Ocean Sci., 12, 743-769, doi:10.5194/os-12-743-2016, 2016.
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Short summary
The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and meridional overturning circulation. A periodic and idealized configuration of the NEMO model has been designed to represent the key physical processes of a zonal portion of the Southern Ocean. Challenging issues concerning how numerical models are able to represent interior mixing forced by high-frequency winds are exposed and discussed, particularly in the context of the overturning circulation.
The aim of this study is to clarify the role of the Southern Ocean storms on interior mixing and...
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