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SUMMARY:Fronts and frontogenesis: a generalised model - Callum Shakespeare
  (DAMTP\, University of Cambridge)
DTSTART:20140402T140000Z
DTEND:20140402T150000Z
UID:TALK51360@talks.cam.ac.uk
CONTACT:Dr Dan Jones
DESCRIPTION:Density fronts are common features at the ocean surface. Field
  observations and numerical simulations have shown that the sharpening of 
 frontal gradients\, or frontogenesis\, can spontaneously generate inertia-
 gravity waves. Although significant progress has been made in describing f
 rontogenesis using quasi-balanced approximations\, most notably semi-geost
 rophic theory (Hoskins\, 1982)\, these models omit waves. In this talk I w
 ill present a new model of frontogenesis that describes the spontaneous ge
 neration of inertia-gravity waves from an initially balanced front. A key 
 feature of the model is that it permits large strains (i.e. on the order o
 f the inertial frequency)\, meaning that it is applicable to the ocean sub
 mesoscale. The model predicts wave emission due to frontogenesis to be exp
 onentially small for small values of strain but significant for larger\nst
 rains. Furthermore\, generated waves are trapped by the oncoming strain fl
 ow and can only be released when the strain field weakens\, leading to wav
 e emission that is strongly localised in both time and space. The analytic
 al results compare well with the output of fully non-linear numerical simu
 lations.
LOCATION:British Antarctic Survey\, Room 307
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