Routes to energy dissipation for geostrophic flows in the Southern Ocean

• Published in: Nature Geoscience
• Main Authors: Nikurashin, M, Vallis, GK, Adcroft, A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2013
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: https://doi.org/10.1038/NGEO1657; http://ecite.utas.edu.au/82710

The ocean circulation is forced at a global scale by winds andfluxes of heat and fresh water. Kinetic energy is dissipated atmuch smaller scales in the turbulent boundary layers and in theocean interior1,2, where turbulent mixing controls the transportand storage of tracers such as heat and carbon dioxide3,4. Theprimary site of wind power input is the Southern Ocean, wherethe westerly winds are aligned with the Antarctic CircumpolarCurrent5. The potential energy created here is converted into avigorous geostrophic eddy field through baroclinic instabilities.The eddy energy can power mixing in the ocean interior68, butthe mechanisms governing energy transfer to the dissipationscale are poorly constrained. Here we present simulations thatsimultaneously resolve meso- and submeso-scale motions aswell as internalwaves generated by topography in the SouthernOcean. In our simulations, more than 80% of the wind powerinput is converted from geostrophic eddies to smaller-scalemotions in the abyssal ocean. The conversion is catalysedby rough, small-scale topography. The bulk of the energy isdissipated within the bottom 100m of the ocean, but about20% is radiated and dissipated away from topography inthe ocean interior, where it can sustain turbulent mixing. Weconclude that in the absence of rough topography, the turbulentmixing in the ocean interiorwould be diminished.