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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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John C. Fyfe, Oleg A. Saenko, Kirsten Zickfeld, Michael Eby, and Andrew J. Weaver

1. Introduction The higher-than-expected warming of intermediate-level waters in the Southern Ocean in recent decades ( Gille 2002 ) has been reproduced in the latest series of global climate model simulations, which include time-varying changes in anthropogenic greenhouse gases, sulfate aerosols, and volcanic aerosols in the earth’s atmosphere ( Fyfe 2006 ). The agreement between observations and state-of-the-art global climate models suggests significant human influence on Southern Ocean

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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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M. J. Manton, Y. Huang, and S. T. Siems

. On the other hand, they both lie in the midst of the Southern Ocean, which is the one region of the global atmosphere and ocean where the effects of landmasses are minimal. The region from 65° to 35°S is our best approximation to an aquaplanet ( Fig. 1 ). However, the landmasses of South America, southern Africa, and Australasia (as well as the Antarctic Peninsula) are likely to introduce some longitudinal variations in climate. Latitudinal variations will be driven at least by the large

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Liping Zhang, Thomas L. Delworth, Sarah Kapnick, Jie He, William Cooke, Andrew T. Wittenberg, Nathaniel C. Johnson, Anthony Rosati, Xiaosong Yang, Feiyu Lu, Mitchell Bushuk, Colleen McHugh, Hiroyuki Murakami, Fanrong Zeng, Liwei Jia, Kai-Chih Tseng, and Yushi Morioka

1. Introduction The Southern Ocean (SO) distributes climate signals among the Atlantic, Pacific, and Indian Ocean Basins through its strong and eastward flowing Antarctic Circumpolar Current (ACC) ( Fig. 1a ), which plays a fundamental role in our climate system. In the current paper, we define the SO as the area south of 50°S, mainly referring to the subpolar region. The dynamics in the SO associated with the transformation of upwelled deep waters into dense Antarctic Bottom Water (AABW

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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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Sarah T. Gille

1. Introduction The Southern Ocean is a sparsely sampled section of the global oceans. Not only is it large and accessible from only a few ports, but it is also an inhospitable environment, with high sea states forced by the strongest winds in the world. As a result, temperature data collected by research vessels over the past few decades contain numerous gaps, which impede assessment of Southern Ocean and overall Southern Hemisphere temperature change. Southern Hemisphere uncertainties are

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