Interaction between a Quasi-Geostrophic Buoyancy Filament and a Heton

Type Article
Date 2017-09
Language English
Author(s) Reinaud Jean N.1, Carton Xavier2, Dritschel David G.1
Affiliation(s) 1 : Univ St Andrews, Sch Math & Stat, St Andrews KY16 9AJ, Fife, Scotland.
2 : UBO UBL, IUEM, Lab Oceanog Phys & Spatiale, F-29280 Plouzane, France.
Source Fluids (2311-5521) (Mdpi), 2017-09 , Vol. 2 , N. 3 , P. 37 (19p.)
DOI 10.3390/fluids2030037
WOS© Times Cited 5
Note This article belongs to the Collection Geophysical Fluid Dynamics
Keyword(s) quasi-geostrophy, surface buoyancy anomaly, vortex dynamics

We investigate the interaction between a heton and a current generated by a filament of buoyancy anomaly at the surface. Hetons are baroclinic dipoles consisting of a pair of vortices of opposite signs lying at different depths. Such structures have self-induced motion whenever the pair of vortices are offset horizontally. A surface buoyancy filament generates a shear flow since the density perturbation locally modifies the pressure field. The vertical shear induced by the filament offsets the vortices of the heton if vertically aligned initially. Moreover, if the vortex nearer the surface is in adverse horizontal shear with the buoyancy filament, the heton tends to move towards the filament. Conversely, if the upper vortex is in cooperative horizontal shear with the buoyancy filament, the heton moves away from it. The filament is also naturally unstable and eventually breaks into a series of billows as it is perturbed by the heton. Moderate to large intensity surface buoyancy distributions separate the vortices of the heton, limiting its advection as a baroclinic dipole. Instead, the vortices of the heton start to interact strongly with surface billows. Additionally, the vortices of the heton can be partially destroyed by the filament if the shear it induces is sufficiently large.

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