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SUMMARY:Jet formation and transport in baroclinic turbulence with simple t
 opography - Thompson\, AF (Cambridge)
DTSTART:20081208T100000Z
DTEND:20081208T103000Z
UID:TALK15624@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:Jets are a well-known feature of the Southern Ocean's Antarcti
 c Circumpolar Current. Evidence from satellite altimetry and numerical mod
 els suggests that zonal jets are also a robust feature of the mid-latitude
  ocean basins. The characteristics of mid-latitude and Southern Ocean jets
  differ significantly\, with the latter having narrow\, ribbon-like appear
 ances and a greater tendency to merge\, migrate and meander. Topography\, 
 lack of meridional boundaries\, and variations in the strength and vertica
 l structure of mean flows all contribute to the dissimilarity of mid-latit
 ude and Southern Ocean jets.\n\nThis study considers the influence of simp
 le topography--sinusoidal ridges and bumps--on the formation and transport
  properties of coherent structures (jets and eddies) in forced-dissipative
 \, quasi-geostrophic turbulence. The experimental framework is a series of
  two-layer\, baroclinically-unstable simulations in a doubly-periodic doma
 in. Transport and mixing properties are diagnosed using the Nakamura effec
 tive diffusivity. In simulations with zonal ridges\, the upper layer\, in 
 particular\, feels a competition between the imposed topographical scale (
 ridge separation) and the Rhines scale. This can lead to unsteady jet stru
 cture and vertical misalignment of transport barriers. Three-dimensional t
 opography with a sufficiently large amplitude may induce periodic bursts o
 f high eddy kinetic energy related to baroclinic instability acting on top
 ographically steered non-zonal mean flows. These episodes allow large-scal
 e reorganization of the jet structure. It is likely that these features pl
 ay a key role in the dynamic nature of Southern Ocean jets.
LOCATION:Seminar Room 1\, Newton Institute
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