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CATEGORIES:Quantitative Climate and Environmental Science Sem
 inars
SUMMARY:Downwelling in Basins Subject to Buoyancy Loss - C
 laudia Cenedese (Woods Hole Oceanographic Institut
 ion)
DTSTART;TZID=Europe/London:20120312T130000
DTEND;TZID=Europe/London:20120312T140000
UID:TALK36892AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/36892
DESCRIPTION:Recent observational\, theoretical\, and modeling 
 studies all suggest that the upper part of the dow
 nwelling limb of the thermohaline circulation is c
 oncentrated in strong currents subject to buoyancy
  loss near lateral boundaries. This is fundamental
 ly different from the traditional view that downwe
 lling takes place in regions of deep convection. E
 ven when resolving the buoyant boundary currents\,
  coarse resolution global circulation and climate 
 models rely on parameterizations of poorly known t
 urbulent mixing processes. In this study\, the fir
 st direct measurements of downwelling occurring wi
 thin a basin subject to buoyancy loss are obtained
 . Downwelling\nis observed near the basin's vertic
 al wall within the buoyant boundary current flowin
 g cyclonically around the basin. Although the enti
 re basin is cooled\, downwelling is absent in the 
 basin interior. Laboratory rotating experiments ar
 e conducted to explicitly resolve the turbulent mi
 xing due to convective plumes\, the baroclinic edd
 ies generated by the boundary current\, and identi
 fy where downwelling takes place. Hence\, in the l
 aboratory small\nvertical velocities can be measur
 ed more reliably than in many numerical calculatio
 ns\, while the measurement of these small vertical
  velocities is still a challenge for field experim
 ents. Downwelling is observed to occur near the ve
 rtical wall within a boundary layer with a thickne
 ss that scales with the Rossby radius of deformati
 on\, consistent with the dynamical balance propose
 d by a previous numerical study. Hence\, downwelli
 ng in the Labrador\nSea and Lofoten Basin cyclonic
  boundary currents may be concentrated in a Rossby
  deformation thick boundary layer in regions with 
 large eddy generation.
LOCATION:MR14\, Centre for Mathematical Sciences
CONTACT:Doris Allen
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