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Yang Jiao and W. K. Dewar

mesoscale flow over rough topography energizes the internal wave field at rates similar to those observed by Naviera-Garabato et al. (2004) in the Southern Ocean. Of direct relevance to this study, Dewar et al. (2015) argued that eastern boundary currents appeared capable of directly driving mixing by centrifugal instability (CI). The sequence of events leading to mixing were that poleward-flowing currents, like the California Undercurrent (CUC; see Fig. 1 ), develop strips of strong negative

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A. M. Treguier, C. Lique, J. Deshayes, and J. M. Molines

Bryan (1986) . The dynamics of the Gulf Stream and its eddy fluxes are often considered in the framework of a free eastward jet subject to baroclinic instability. In the classical models, such as Phillips or Charney’s (e.g., Pedlosky 1979 ), instability leads to the development of waves and eddies and thus generates a cross-jet eddy heat flux that tends to reduce the temperature gradient across the front. However, the Gulf Stream is a western boundary current, much more complex than a free zonal

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Audrey Delpech, Claire Ménesguen, Yves Morel, Leif N. Thomas, Frédéric Marin, Sophie Cravatte, and Sylvie Le Gentil

poorly understood. Different physical mechanisms have been proposed to explain their formation, relying on a cascade of mechanisms transferring energy from a deep energy source (generally generated through the propagation at depth of atmospheric variability or currents instabilities) to the mean jet-structured circulation (see Fig. 2 of Ménesguen et al. 2019 ). Earlier studies have shown that two-dimensional turbulence induces an inverse cascade, with energy transferred toward larger scales. On a

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Alain Colin de Verdière and Michel Ollitrault

-scale barotropic structures ( Rhines 1977 ; Salmon 1980 ). The barotropic circulation can then be seen as the end product of these turbulent cascades. Its determination in eddy-rich regions, such as the western boundary inertial recirculation regions or the Antarctic Circumpolar Current (ACC), can become a useful benchmark for judging whether the nonlinear interactions are operating correctly in ocean eddy–resolving models. The baroclinic velocities are obtained locally from the thermal wind equation. The

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W. K. Dewar, J. C. McWilliams, and M. J. Molemaker

-stratified fluids . J. Fluid Mech. , 289 , 115 – 128 , doi: 10.1017/S002211209500125X . Wirth , A. , and B. Barnier , 2008 : Mean circulation and structures of tilted ocean deep convection . J. Phys. Oceanogr. , 38 , 803 – 816 , doi: 10.1175/2007JPO3756.1 . Wright , C. , R. Scott , B. Arbic , and D. Furnival , 2012 : Bottom dissipation of subinertial currents at the Atlantic zonal boundaries . J. Geophys. Res. , 117 , C03049 , doi: 10.1029/2011JC007702 . Young , W. , 2010 : Dynamic

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François Ascani, Eric Firing, Julian P. McCreary, Peter Brandt, and Richard J. Greatbatch

wave forced at the equator along the western boundary, a process mimicking the instabilities associated with the equatorial crossing of the deep western boundary current (DWBC) in the Atlantic Ocean. In this case (which is more thoroughly studied by d’Orgeville et al. 2007 ), EDJ-like currents are also generated, propagating into the interior and forming low-frequency equatorial basin modes. In this scenario, the vertical scale of the EDJs does not depend on the basin width, so the appearance of

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Thomas Meunier, Enric Pallàs Sanz, Miguel Tenreiro, José Ochoa, Angel Ruiz Angulo, and Christian Buckingham

1. Introduction Loop Current eddies (LCEs) are large (up to 200 km in radius) and energetic anticyclonic rings that detach sporadically from the Loop Current (e.g., Austin 1955 ; Leipper 1970 ; Leben 2005 ; Xu et al. 2013 , among others), carrying Subtropical Underwater (SUW) as they drift westward across the Gulf of Mexico (GoM) ( Cooper et al. 1990 ; Forristall et al. 1992 ). The SUW’s properties sharply contrast with the Gulf Common Water (GCW) and are evident as a warm and salty (i

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Nils Brüggemann and Carsten Eden

to approximately 10%, while additional modes also occur that are unbalanced to an even higher degree. Values of Ri = O (1) can be found at the ocean surface with weak stratification or within strong boundary currents with large velocity shears. Simulations of an idealized subtropical, eastern boundary current system by Capet et al. (2008a) and Capet et al. (2008b) reveal submesoscale eddies and filaments out of geostrophic balance in the upper 100 m. Furthermore, Capet et al. (2008c

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J. H. LaCasce and J. Wang

surface boundary conditions: where b s is the surface buoyancy. Thus, only the SQG solution is directly linked to the surface density. For the bottom boundary condition, W13 demanded that the vertical derivative of both streamfunctions vanish and that the total velocity be zero at the bottom. Alternately, one can simply require that each streamfunction vanish with depth (e.g., Lapeyre and Klein 2006 ; LaCasce and Mahadevan 2006 ; Lapeyre 2009 ): It turns out that using this condition greatly

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Thomas Meunier, Claire Ménesguen, Richard Schopp, and Sylvie Le Gentil

, recent studies have shown that they were often linked to smaller cyclonic structures detaching simultaneously from the boundary current ( Carton et al. 2002 ; Barbosa Aguiar et al. 2013 ). This detachment usually occurs in the vicinity of the major topographic features of the Iberian coast such as Cape São Vicente and the Estremadura promontory ( Bower et al. 1997 ). They then drift southwestward and can travel more than 1000 km away from the eastern boundary and reach lifetimes of more than 2 yr

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