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Paola Cessi and Maurizio Fantini

to the surface and diffusion as the only means to transmit temperature gradients downward, the circulation is confined to a thermocline of thickness h, which according to (5) scales as Welander (1971) refined Munk's scaling by estimating the broad upwelling driven by differential surface heating. His scaling considers the meridional circulation υ driven by the large-scale upwelling w . The amplitude of w is set by the continuity equation, υ x + υ y + w z = 0, (7) so that Continents

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Laurie L. Trenary and Weiqing Han

the east—and remote forcing from the Pacific via the ITF, we perform and analyze various diagnostic experiments using an ocean general circulation model and a linear ocean model. Particular emphasis is placed on the TRIO region where thermocline variability is suggested to affect sea surface temperature and thus climate. This paper is organized as follows. Section 2 describes the ocean models used, experimental procedure, and datasets. Section 3a presents model–data comparisons; sections 3b

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Haijun Yang and Lu Wang

variations in the high latitudes could induce changes in the deep-water formation, causing variations in the Atlantic meridional overturning circulation (AMOC), which affect the tropical Atlantic and beyond ( Chang et al. 2008 ). A recent observational study confirms that the Labrador seawater thickness change can significantly affect the tropical western boundary currents between the lower thermocline and intermediate level through coastal Kelvin waves ( Zhang et al. 2011 ). In the Atlantic, the

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Jeffery R. Scott and Jochem Marotzke

location. Using an idealized single-hemisphere ocean general circulation model, Cummins et al. (1990 , hereafter CHG) parameterized vertical diffusivity as a function of the buoyancy frequency, effectively increasing mixing at depth, particularly below the thermocline. Cummins (1991) examined the results of several additional runs with specified increased mixing below the thermocline. Using a similar model without wind forcing, Marotzke (1997 , hereafter M97) imposed mixing only along the

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William K. Dewar

parameterization, were shown to develop propagation tendenciesthat could be related to straightforward measures oftheir structure. It was this propagation tendency thatwas balanced against the Sverdrup flow at the intergyreboundary. Calculation of the thermocline away fromthe intergyre boundary required explicit considerationof the front trajectory through the general circulation,as well as potential vorticity conservation. It was shownthat the arrested front solutions in Dewar ( 1991 ) belongto a class of

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Niklas Schneider

, density-compensated temperature and salinity ( T – S ) anomalies are introduced into the ocean thermocline, such that the circulation carries them to the equatorial outcrop regions. Two experimental designs are considered: perturbations of the initial conditions and continual, in situ generation. As an initial value problem, spiciness anomalies have to be staged upstream of the equatorial upwelling regions such that emerging T – S perturbations are of approximately constant magnitude for the

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Joke F. Lübbecke and Michael J. McPhaden

basinwide zonal wind stress anomalies. The weakened response of zonal wind stress to SST anomalies is due to the cooler mean SST in the eastern equatorial Pacific that results in reduced mean convection and a westward shift in the ascending branch of the Walker circulation. The weakened thermocline slope response to zonal wind stress anomalies can be attributed to a smaller zonal wind fetch in the more recent time period due to ENSO-related wind anomalies being more confined to the western basin. It

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Zhengyu Liu

time scale of barotropic Rossby waves(about one week) to achieve a new steady balance, leaving little thermocline variability. The evolution ofthermocline structure and circulation differs dramatically between a spinup and a spindown.For instance, with a change in the Ekman pumping field, the lower-layer fluid in the shadow zone is no longermotionless. After a spinup, the lower-layer water moves southward because of the compression on planetaryvortex tubes by the downward anomalous Ekman pumping

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Young-Gyu Park

advective–diffusive buoyancy balance in the thermocline ( Bryan and Cox 1967 ; Welander 1971 ) suggests a nonlinear mass transport relation, Ψ ∼ Δ ρ 1/3 , for the oceanic thermohaline circulation. The details of the scaling law and studies supporting the scaling law and the difference between the linear and nonlinear relations are described in section 2 . This scaling law does not add any real complexity to Stommel’s classical two-box thermohaline circulation model, but it does change some of the

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Tong Lee, Ichiro Fukumori, Dimitris Menemenlis, Zhangfan Xing, and Lee-Lueng Fu

thermocline timescales for mid- and high-latitude oceans, but is relatively sufficient for the development of circulation systems in upper tropical oceans, which is the main focus of the present study. The relatively short spinup time alleviates the drift of density structure in the deep ocean (a common problem for ocean models) without using relaxation of deep density to climatology, which sacrifices model dynamics. The short spinup and real-time integration period precludes the analysis of ITF effect on

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