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Title : A Mechanism for the Formation of ``Storm Tracks" in the Southern Ocean
Name of the speaker : Chris Chapman
Affiliation : LOCEAN
Laboratory organizer : LOCEAN
Date and time : 15-10-2014 11h00
Location : UPMC, 4 place Jussieu, Paris 5e, salle de réunion LOCEAN, tour 45/55, 4eme étage
Summary :

"Storm Tracks", localised regions of anomalously high meso-scale eddy activity, are found throughout the Southern Ocean, but most commonly downstream of large topographic features such as the Campbell and Kergulen Plateaus, where the Antarctic Circumpolar Current flow are strongly steered. Storm tracks are important: they act to concentrate the mixing and poleward transport of tracers in particular regions and provide a strong forcing on the mean flow. Both of these effects may impact the climate system on short and long time scales.

In this seminar, a new mechanism for the initiation and downstream development of Southern Ocean storm tracks is proposed. Our mechanism is taken from a similar theory used to explain similar ``storm track" phenomena in the mid-latitude atmosphere. To study these Southern Ocean storm tracks, was employ a wind-driven, isopycnal, primitive equation model with idealised bottom topography and a extremely powerful, but little known diagnostic (in oceanography at least): the wave-activity flux (related to the Eliassen--Palm flux and eddy energy budgets).

In this seminar, I will give first give a short introduction to the wave-activity flux. I will then show how it can be used to diagnose the influence of different dynamical effects in our ocean model. Finally, I will assemble the pieces to present a simple, conceptual framework for understanding the physics of storm tracks.