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SUMMARY:Physical Limnology: A review - Jorg Imberger (Western Australia)
DTSTART:20081030T140500Z
DTEND:20081030T151500Z
UID:TALK14330@talks.cam.ac.uk
CONTACT:Doris Allen
DESCRIPTION:Over the last 30 years\, limnology has become a mature field w
 ith most of the energy flux paths now well established and incorporated in
 to 3D models. The energy from the wind and the sun enters a lake via the f
 ree surface\, the river inflow may form overflows\, intrusions or underflo
 ws and the selectivity of a withdrawal flow depends strongly on the therma
 l stratification in the lake. The talk is structured to follow the energy 
 flux from the wind\, to surface waves and surface layer turbulence\, to ba
 sin scale barotropic lake seiching and internal waves\, to high frequenc
 y free internal waves and free gyres\, to the benthic boundary layer to fi
 nally the intermittent turbulence field in the water column\; this is gene
 rated by non linear wave breaking\,  Kelvin Hemholz billowing and Holmboe
  shear instabilities\, depending on the relative placement of the shear an
 d density field gradients. Inflows and outflow dynamics is then briefly re
 viewed. Next\, I show how this symphony of motions adds to sustain a weak 
 vertical mass flux and a horizontal dispersion\; the latter being critical
 ly dependent on the topology of the horizontal residual circulation and th
 e presence of unsteady stagnation points. I will conclude with an illustra
 tion of how the full complexity of these motions can be captured with a 3D
  model that also beautifully illustrates the competitive nature of the var
 ious components of the motion in determining the net mixing in a lake and 
 I show how this competition is a strong function of the lake and stratific
 ation properties.
LOCATION:MR15\, Centre for Mathematical Sciences
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