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Dhruv Balwada, Joseph H. LaCasce, Kevin G. Speer, and Raffaele Ferrari

dispersion in the western Atlantic was either local or driven by mean flow shear up to scales of approximately 100km, while the particle pairs separated diffusively in the eastern Atlantic. Ollitrault et al. (2005) also reported local stirring between 40 and 300 km, and some indications of nonlocal stirring at shorter scales. In this study, we examine stirring at length scales of 5–100 km and depths of 500–2000 m in the southeast Pacific Ocean sector of the Antarctic Circumpolar Current (ACC), using

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Louis-Philippe Nadeau and Raffaele Ferrari

topography and on the connection to the ocean basins to the north. Over the last 20 years, it has become clear that geostrophic eddies are an additional crucial aspect of ACC dynamics ( Marshall and Speer 2012 ), but we are still far from having a theory of the ACC transport as complete as Sverdrup’s theory for the transport of the western boundary currents along continental margins ( Pedlosky 1996 ). The emerging consensus is that the ACC vertically integrated zonal transport is set by a balance of

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Byron F. Kilbourne and James B. Girton

1. Introduction The study of near-inertial oscillations and internal waves began with the advent of moored, self-recording current meter measurements in the 1960s. These instruments revealed considerable variance near the local inertial frequency ( Webster 1968 ) and motivated a series of efforts to better understand near-inertial variability, its predominant generation mechanisms, and its role in other ocean processes such as diapycnal mixing and energy transport: Pollard and Millard (1970

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J. Alexander Brearley, Katy L. Sheen, Alberto C. Naveira Garabato, David A. Smeed, and Stephanie Waterman

1. Introduction In situ and satellite altimetric observations have shown that the ocean kinetic energy (KE) field in mid-to-high latitudes is dominated by mesoscale eddies on scales of 50–100 km. Maps of eddy kinetic energy (EKE; e.g., Wunsch and Stammer 1998 ), reveal an intensification of EKE in regions of large mean flows such as the Antarctic Circumpolar Current (ACC) as a result of baroclinic instability ( Smith 2007 ), with a particular enhancement of EKE in frontal zones and immediately

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Ross Tulloch, Raffaele Ferrari, Oliver Jahn, Andreas Klocker, Joseph LaCasce, James R. Ledwell, John Marshall, Marie-Jose Messias, Kevin Speer, and Andrew Watson

, possibly because models underestimate the current temporal variability or because observational estimates are biased high due to poor temporal sampling especially at depth. We show below that tracers injected in the model move eastward at the same rate as the tracer released in DIMES, further confirming that the model eastward transport is consistent with observations. The initial and boundary conditions in the Drake Patch are derived from the 1° × 1° OCCA climatology that does not resolve eddies. Upon

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Matthew R. Mazloff, Raffaele Ferrari, and Tapio Schneider

western boundary currents and surface wind-driven flows close the mass and momentum budgets. Mechanical forcing is weak poleward of Drake Passage in the Ross and Weddell Polar Gyres. The overturning in these latitudes consists primarily of the SO abyssal cell, though at these latitudes the “abyssal cell” spans all depths. With the exception of the weaker wind-driven flow, the balance in this region is much like in the subtropical gyre, consisting of a mean geostrophic volume transport with significant

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F. Sévellec, A. C. Naveira Garabato, J. A. Brearley, and K. L. Sheen

motions; e.g., Polzin et al. 1997 ; D’Asaro et al. 2007 ; Waterman et al. 2013 ; Sheen et al. 2013 ) to near-bottom frictional Ekman currents along sloping topographic boundaries ( Garrett et al. 1993 ), wind-driven Ekman motions, and rectified mesoscale eddy flows along sloping isopycnals ( Marshall and Speer 2012 , and references therein). The latter two mechanisms are believed to extensively underpin vertical flow in the Southern Ocean, a region hosting a prominent large-scale vertical

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Dhruv Balwada, Kevin G. Speer, Joseph H. LaCasce, W. Brechner Owens, John Marshall, and Raffaele Ferrari

Atlantic Deep Water (NADW), flows south in a deep western boundary current and eventually spreads along the northern flank of the Antarctic Circumpolar Current (ACC) on its course to the Indian and Pacific Ocean basins. A fraction of NADW is injected into the ACC in layers below the Drake Passage sill depth and can be transported across the ACC in deep geostrophic boundary currents to upwell into regions of surface buoyancy loss and to be transformed into Antarctic Bottom Water (AABW). This AABW and

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Michael Bates, Ross Tulloch, John Marshall, and Raffaele Ferrari

surface height and assuming geostrophic balance, except within 5° of latitude of the equator, where a β -plane formulation of geostrophic balance is used following Lagerloef et al. (1999) . The global map of is shown in Fig. 2a . Western boundary currents (WBCs), like the Gulf Stream, Kuroshio, East Australia Current, Agulhas Current, and Antarctic Circumpolar Current (ACC), are prominent kinetic energy maxima. The discontinuities across ±5° of latitude reflect the transition from the f -plane

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L. St. Laurent, A. C. Naveira Garabato, J. R. Ledwell, A. M. Thurnherr, J. M. Toole, and A. J. Watson

. 1997 ; Ledwell et al. 2000 ). Typically located in the middle of oceanic basins away from enhanced boundary currents, the tides are often the largest source of energy at midocean ridge sites. Tidal flow incident on bathymetry leads to an internal wave response, principally at tidal frequencies ( St. Laurent and Garrett 2002 ), that can radiate energy into the deep interior of the ocean. As internal waves radiate, they lose energy through a variety of instability and scattering mechanisms ( Munk

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