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SUMMARY:Rates and mechanisms of turbulent dissipation and mixing in the So
 uthern Ocean: Results from the DIMES experiment - Dr. Katy Sheen\, Univers
 ity of Southampton 
DTSTART:20121017T120000Z
DTEND:20121017T130000Z
UID:TALK41076@talks.cam.ac.uk
CONTACT:Dr Andrew Meijers
DESCRIPTION:Small-scale turbulent motions in the Southern Ocean play a vit
 al role in setting the abyssal stratification and in determining the respo
 nse of climate models to anthropogenic forcing. However\, few direct obser
 vations of turbulent mixing in the Antarctic Circumpolar Current (ACC) exi
 st. Further more\, observations of the sources and mechanisms underlying t
 he intensity and distribution of turbulent kinetic energy dissipation in t
 he ACC are scarce. Consequently in 2009\, the Diapycnal and Isopycnal Mixi
 ng Experiment in the Southern Ocean (DIMES)\, was initiated. DIMES is a mu
 tli-component US/UK project focused on understanding patterns and processe
 s of mixing in two contrasting regimes (the SE Pacific and the SW Atlantic
 ) of the ACC.  \n\nIn this presentation\, we report on turbulent mixing ob
 servations collected using free-falling microstructure instruments as part
  of the DIMES experiment. Turbulent dissipation rates\, which vary between
  ~10-10 W kg-1 and ~10-9 W kg-1\, are found to be strongly related to the 
 strength of bottom current speeds and the local topographic roughness. Thi
 s observation\, alongside detailed analysis of internal wave field propert
 ies\, supports the hypothesis that abyssal turbulent dissipation is attrib
 uted to the breaking of internal waves generated by ACC - topography inter
 actions. However\, local turbulent dissipation accounts for only a small p
 roportion of the energy flux predicted by linear theory\, opening question
 s as to the fate of much of the bottom-generated internal wave energy. Thi
 s study represents the largest comparison of turbulent dissipation measure
 ments and internal wave characteristics in the Southern Ocean\, to date.\n
LOCATION:British Antarctic Survey\, Room 307
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