Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean
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° ...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-06-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/12/743/2016/os-12-743-2016.pdf |
| 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 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<sup>−10</sup>–10<sup>−9</sup> W kg<sup>−1</sup>) 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 Δ<i>x</i> = 1 km. |
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| ISSN: | 1812-0784 1812-0792 |