Dissipation of the energy imparted by mid-latitude storms in the Southern Ocean

• Published in: Ocean science 2016-01, Vol.2016, p.1
• Main Authors: Jouanno, J, Capet, X, Madec, G, Roullet, G, Klein, P, Masson, S
• Format: Article
• Language: English
• Subjects: Comparative analysis; Oceans; Storms; Thermohaline circulation
• ISSN: 1812-0784; 1812-0792

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° S 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. 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.sup.−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 modelling exhibits important delicacies owing to a lack of convergence of key components of its energetics even when reaching Δx = 1 km.