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SUMMARY:Diapycnal mixing in Drake Passage - Andy Thompson\, UEA
DTSTART:20070911T100000Z
DTEND:20070911T110000Z
UID:TALK7871@talks.cam.ac.uk
CONTACT:Deb Shoosmith
DESCRIPTION:Theories of the Southern Ocean circulation generally assume th
 at flow is along rather than across isopycnals (surfaces of constant densi
 ty) in the ocean interior\, with diapycnal (across density surfaces) proce
 sses limited to the ocean's mixed layer.  Recently\, though\, observationa
 l studies have found evidence of large diapycnal mixing near topographical
  features\, which suggests that the assumption of purely isopycnal flow is
  invalid.  In this study\, temperature and salinity profiles obtained with
  expendable CTD (XCTD) probes throughout Drake Passage\, Southern Ocean be
 tween February 2002 and July 2005 are analyzed to estimate turbulent diapy
 cnal eddy diffusivities to a depth of 1000 m.  Diffusivity values are infe
 rred from density/temperature inversions and internal-wave vertical strain
 .  Both methods indicate that mixing in Drake Passage is characterised by 
 strong spatial variability with the Polar Front separating two dynamically
  different regions.  Mixing rates typically exceed open ocean levels\, esp
 ecially north of the Polar Front.  Wind-driven near-inertial waves\, stron
 g mesoscale eddy activity and double-diffusive convection are suggested as
  possible factors contributing to observed mixing patterns. Both the spati
 al variability and the magnitude of the mixing rates across Drake Passage 
 suggest that new models are needed to describe the meridional circulation 
 in the Southern Ocean and its role in the global overturning circulation.
LOCATION:British Antarctic Survey
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