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Richard G. Williams, Vassil Roussenov, M. Susan Lozier, and Doug Smith

formation. Classical gyre theory explains how the large-scale North Atlantic wind pattern drives subtropical and subpolar gyre circulations ( Luyten et al. 1983 ), with the subtropical gyre characterized by downwelling, deepening isotherms and a sharp thermocline (a region of enhanced vertical temperature gradient) and the subpolar gyre characterized by upwelling, a shoaling of the isotherms, and a thin or outcropping thermocline. In this study, the relationship between upper-ocean heat content and

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Eun Young Kwon, Curtis Deutsch, Shang-Ping Xie, Sunke Schmidtko, and Yang-Ki Cho

, circulation, and/or respiration (e.g., Deutsch et al. 2005 , 2006 ) accentuated by the decadal residence time of the thermocline circulation ( Ito and Deutsch 2010 ). Improved understanding of the supply mechanism and its relationship to climate variations will help us better understand observed O 2 changes. As a result of strong stratification within the North Pacific, convection is restricted to relatively shallow depths (usually <250 m; e.g., Suga et al. 2004 ), and the ventilation of deeper layers

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N. J. Burls and A. V. Fedorov

subsurface water in the equatorial and coastal upwelling regions, decreasing the zonal SST gradient ( Fig. 5d ). Consequently, the mean intensity of the atmospheric Walker circulation ( Fig. 6a ) and the easterly trade winds together with the zonal slope of the equatorial thermocline ( Fig. 5d ) all decrease in response to a reduction of extratropical cloud albedo. Similarly, the strength of the Hadley circulation decreases together with the meridional SST gradient ( Fig. 6b ). This reduction in the

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Willem P. Sijp and Matthew H. England

1. Introduction The geometry of the World Ocean is characterized by zonal boundaries interrupted only at the latitudes of the Drake Passage (DP). This semicompartmental distribution of water allows the development of distinct thermocline properties in each basin. In particular, thermocline water of the Atlantic Ocean is more saline than its Pacific counterpart (e.g., Levitus 1982 ). This remarkable feature is fundamental to the ocean’s thermohaline circulation (THC; e.g., Gordon 1986

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Sijia Zou, M. Susan Lozier, and Xiaobiao Xu

1. Introduction The upper limb of the Atlantic meridional overturning circulation (AMOC) transports warm, saline waters northward in the upper layer to the subpolar/subarctic North Atlantic, where they are transformed into cold, fresh waters that flow southward in the deep limb. Due to its role in redistributing heat, freshwater, and carbon, the AMOC and its variability have significant impacts on the Earth climate system, including European climate ( Stouffer et al. 2006 ), North Atlantic

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Wei Liu, Zhengyu Liu, and Esther C. Brady

the Atlantic ( Fig. 5b ). It is this increased upper-ocean salinity that is transported northward by the upper limb of the mean AMOC (upper 1000 m, Fig. 5b ), corresponding to an equivalent freshwater export to the south and therefore enhanced M ovS export in ADJ (relative to CTL). This relationship between the tropical bias and the M ovS export should be robust because it is determined by the thermocline circulation of tropical–extratropical exchange ( Liu et al. 1994 ) in the South Atlantic

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Darryn W. Waugh, Andrew McC. Hogg, Paul Spence, Matthew H. England, and Thomas W. N. Haine

along- or across-isopycnal transport. We first examine the possibility that the wind stress perturbations lead to a change in the strength of the mean horizontal circulation, which in turn leads to a changes in along-isopycnal transport and ages within the thermocline. Changes in the horizontal circulation in the perturbation simulations are examined using the (depth-integrated) barotropic streamfunction (BSF), which is a commonly used indicator of the horizontal subtropical gyre circulation. A

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Hartmut H. Hellmer, Frank Kauker, Ralph Timmermann, and Tore Hattermann

twentieth century, is indicated by the dashed orange arrow. The positions of the profiles used for analyzing the processes across the Filchner Trough Sill (FTS) ( Fig. 9 ) are marked as red stars. Inset shows map location within the Southern Ocean. The southern Weddell Sea continental shelf is far from the southern ACC front. A clockwise gyre circulation causes CDW derivatives to enter the Weddell Sea from the east ( Schröder and Fahrbach 1999 ; Ryan et al. 2016 ) and continue as warm deep water (WDW

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Young-Oh Kwon and Claude Frankignoul

1. Introduction The Atlantic meridional overturning circulation (AMOC) is a crucial component of the Atlantic as well as the global climate, for example through its close relationship with the meridional ocean heat transport (e.g., Msadek et al. 2013 ) and the Atlantic multidecadal oscillation (AMO; e.g., Knight et al. 2005 ). Although the AMOC is in nature a three-dimensional circulation, it is commonly studied in two-dimensional space, using the meridional overturning streamfunction, which

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Arthur J. Miller, Daniel R. Cayan, and Warren B. White

al. 1993 ) of cooling in the central North Pacific and warming along the eastern boundary seen in the SST is replaced at depth by a western-intensified structure in the temperature field north of 30°N that is reminiscent of gyre-scale circulation theory (e.g., Pedlosky 1987 ). This subsurface cooling in the Kuroshio Extension area was identified by Deser et al. (1996) and appears to extend up to the surface. We present evidence here that the previously observed local thermocline cooling is

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