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Paul Spence, Oleg A. Saenko, Michael Eby, and Andrew J. Weaver

1. Introduction The upper-ocean meridional overturning circulation (MOC) can be thought of as consisting of two branches ( Gnanadesikan 1999 ). One is associated with deep-water formation in the northern North Atlantic where light waters are converted to dense waters. In the other branch, found in the Southern Ocean and in the low-latitude oceans, the reverse process takes place with dense water being converted back to light water. The two branches can influence each other in that, for example

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Robert Hallberg and Anand Gnanadesikan

1. Introduction The water masses that compose the vast majority of the ocean volume are either formed, modified, or transit through the Southern Ocean ( Sverdrup et al. 1942 ; Schmitz 1996 ; Doney et al. 1998 ). It has long been known that mesoscale eddies play an important role in the dynamics of this region ( Johnson and Bryden 1989 ; Marshall et al. 1993 ; Killworth and Nanneh 1994 ; Marshall and Radko 2003 ). This paper explores how these eddies determine not only the magnitude and

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David K. Hutchinson, Andrew Mc C. Hogg, and Jeffrey R. Blundell

approximation becomes far less accurate because ocean surface velocities become comparable with wind velocities. Pacanowski (1987) pointed out that in equatorial regions, | u o | ∼ 1 m s −1 and | u a | ∼ 6 m s −1 , so that the use of τ 0 introduces errors in τ of up to 30%. However, in most parts of the ocean, including the Southern Ocean, wind speed is at least an order of magnitude larger than the ocean currents, thus the inclusion of u o in the wind stress parameterization is a second

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Adele K. Morrison and Andrew McC. Hogg

1. Introduction The overturning of deep, carbon rich water masses in the Southern Ocean is closely linked to the outgassing rate of natural CO 2 , and hence future changes in upwelling may significantly impact the present-day global oceanic sink of atmospheric CO 2 . The strong link between outgassing and overturning ( Toggweiler et al. 2006 ) has led to the suggestion that the Southern Ocean sink has weakened in response to increased westerly winds, owing to an inferred enhancement of the

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Jan D. Zika, Bernadette M. Sloyan, and Trevor J. McDougall

Current (ACC) where vigorous winds of the Southern Hemisphere provide the energy required to convert dense water to light [see Kuhlbrodt et al. (2007) , for a comprehensive review]. The Southern Ocean links the three major ocean basins and it is there that many water masses are either formed or modified ( Sverdrup et al. 1942 ). The ACC is a zonal current, circulating around Antarctica, with a transport of 134 ± 13 Sv (Sv = 10 6 m 3 s −1 ) as measured through the Drake Passage ( Whitworth 1983

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Matthew R. Mazloff, Patrick Heimbach, and Carl Wunsch

1. Introduction The Southern Ocean circulation is dynamically distinct from all other ocean regions in that it is characterized by a strong circumpolar current ( Crease 1964 ). The region also has a known strong temporal variability ( Gille and Kelly 1996 ; Wunsch and Heimbach 2009 ). Its remoteness and distinctiveness have greatly inhibited both observations and dynamical understanding of the controls on its circulation and corresponding properties such as freshwater transports. Various

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Daniele Iudicone, Sabrina Speich, Gurvan Madec, and Bruno Blanke

1. Introduction According to de Santillana and von Dechend (1992) , some ancient cosmogonies consider the existence of a “mother fountain of all the waters of the world” (that is a confluence of all the existing waters, which rise and return there after completing their courses) and, interestingly, locate this fountain in the Southern Ocean. In the more recent classical “global conveyor belt” picture of the global ocean circulation, the nucleus is instead in the North Atlantic Ocean and

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Andrew McC. Hogg, Paul Spence, Oleg A. Saenko, and Stephanie M. Downes

1. Introduction The circulation of the Southern Ocean is characterized by strong eastward zonal flow [the Antarctic Circumpolar Current (ACC)]. The baroclinic component of the ACC is associated with isopycnal layers that slope up toward the surface in the south, thereby connecting the deep and abyssal ocean with surface waters ( Morrison et al. 2015 ). This isopycnal slope is maintained in part by the strong westerly wind stress at the surface and provides a conduit by which deep, dense water

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Yueng-Djern Lenn and Teresa K. Chereskin

1. Introduction Circumpolar integration of the Southern Ocean Ekman transport results in estimates ranging from 25 to 30 Sv (1 Sv ≡ 10 6 m 3 s −1 ; Sloyan and Rintoul 2001 ; Speer et al. 2000 ). The Ekman layer thus constitutes the shallowest limb of the meridional overturning circulation of the Antarctic Circumpolar Current (ACC), a key component of the coupled ocean–atmosphere climate system ( Deacon 1937 ; Sloyan and Rintoul 2001 ; Speer et al. 2000 ). Despite the large transport

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Mads B. Poulsen, Markus Jochum, James R. Maddison, David P. Marshall, and Roman Nuterman

et al. 1991 ; Ivchenko et al. 1996 ; Olbers 1998 ). This process is fundamental to the dynamics of the Southern Ocean as it causes a net downward momentum transfer which permits a governing momentum balance between surface wind stress and topographic form drag across shallow ridges and continents ( Munk and Palmén 1951 ; Masich et al. 2015 ). For adiabatic and geostrophic eddies the zonal eddy form stress additionally induces a meridional circulation that compensates Southern Ocean wind

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