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Ivana Cerovečki and Matthew R. Mazloff

1. Introduction The Southern Ocean (SO) plays a vital role in the global overturning circulation and global climate because of intense water mass transformation and formation taking place in this region ( Macdonald and Wunsch 1996 ; Sloyan and Rintoul 2001a , b ; Talley et al. 2003 ; Talley 2008 ). In the upper cell of the SO overturning circulation, strong westerly winds drive equatorward Ekman transport and upwelling in the Antarctic Circumpolar Current (ACC). Once at the surface, the

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Byron F. Kilbourne and James B. Girton

al. 2012 ). The Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) is a long-term international tracer release experiment designed to investigate interior mixing in the Antarctic Circumpolar Current (ACC). The studied area extends from the relatively weak and diffuse region of the ACC found in the eastern South Pacific to the more constricted and energetic currents of the Scotia Sea and the South Atlantic. The ship observations presented here come from the first field

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

of these parameterizations are particularly important in the Southern Ocean, where the surface is connected to the deep ocean via sloping isopycnals and along-isopycnal stirring plays a key role in biological production ( Uchida et al. 2019 , 2020 ) and ventilation of the deep ocean ( Marshall and Speer 2012 ; Abernathey and Ferreira 2015 ; Balwada et al. 2018 ; Jones and Abernathey 2019 ). To ensure the fidelity of these parameterizations, it is essential that quantitative estimates of

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Louis-Philippe Nadeau and Raffaele Ferrari

Fig. 15 , are blocked by the major topographic features in the Southern Ocean and can therefore support meridional boundary currents. However, future work will need to explore how to best identify the gyre circulations in the Southern Ocean, where the topography is far more complex than the one used in this study. For example, in the Southern Ocean, the gyre mode may be divided into multiple smaller subdomains defined by the major topographic features (Scotia Ridge, Kerguelen Plateau, Southeast

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Sophia T. Merrifield, Louis St. Laurent, Breck Owens, Andreas M. Thurnherr, and John M. Toole

1. Introduction A number of processes in the Southern Ocean are thought to support high levels of mixing relative to other regions of the global ocean. At the surface, strong winds and storms force the ocean at near-inertial frequencies, generating internal waves that can propagate downward ( Price 1981 ). Upper-ocean and middepth values of diapycnal diffusivity are believed to be set in part by the breaking of these near-inertial waves (e.g., Wu et al. 2011 ). Deep-reaching currents

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Ru Chen, Sarah T. Gille, Julie L. McClean, Glenn R. Flierl, and Alexa Griesel

have been employed to estimate diffusivities in the tropical North Atlantic (e.g., Banyte et al. 2013 ), western boundary currents (e.g., Chen et al. 2014 ), the Southern Ocean (e.g., LaCasce et al. 2014 ; Tulloch et al. 2014 ), and the global surface (e.g., Abernathey and Marshall 2013 ). Understanding the estimated diffusivity patterns is a necessary step toward improving eddy parameterization schemes. A common approach is to interpret the mixing length L mix instead of the diffusivity

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J. R. Ledwell, L. C. St. Laurent, J. B. Girton, and J. M. Toole

remain sparse and mostly limited to mid- and low latitudes ( Gregg et al. 1973 ; Toole et al. 1994 ; Gregg et al. 2003 ; Klymak et al. 2006 ). Measurements of vertical shear and strain at scales of tens of meters, from which mixing estimates can be inferred, are more widespread, but formulations relating these internal wave characteristics to dissipation rates and diapycnal diffusivity are subject to a number of added approximations ( Gregg 1989 ; Kunze et al. 2006 ). The Southern Ocean is a

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Alberto C. Naveira Garabato, Kurt L. Polzin, Raffaele Ferrari, Jan D. Zika, and Alexander Forryan

1. Introduction The meridional overturning circulation and stratification of the global ocean are shaped critically by processes in the Southern Ocean [see Marshall and Speer (2012) and Rintoul and Naveira Garabato (2013) for recent reviews]. The zonally unblocked nature of the Antarctic Circumpolar Current (ACC) system confers the region with a set of special dynamics that ultimately results in the focusing therein of large vertical exchanges between layers spanning the global ocean

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

from constant in space or time but instead exhibits considerable variability (e.g., Davis 1991 ; Holloway 1986 ; Ledwell et al. 1998 ; Marshall et al. 2006 ; Abernathey et al. 2010 ; Naveira Garabato et al. 2011 ). Eddy transfer is thought to be of leading order importance in dynamical balances in the ocean and the distribution of tracers therein, particularly in the Southern Ocean (see Marshall and Speer 2012 ). Therefore, coarse-resolution models that do not resolve mesoscale eddies must

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