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Marc d’Orgeville and W. Richard Peltier

SST, two further ingredients (salinity and atmospheric variability) have been invoked to refine this basic concept. The role of salinity and atmospheric forcing in sustaining such oscillatory behavior has been extensively studied in the context of uncoupled ocean-only general circulation models (see, e.g., Weaver and Sarachik 1991 ; Winton and Sarachik 1993 ). In the present paper, our focus will be on the results delivered by a fully coupled model. A sea surface salinity (SSS) anomaly in the

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Garry K. C. Clarke, Andrew B. G. Bush, and John W. M. Bush

than 5–10 yr. The climate system switch that has received the greatest attention and for which there is the strongest evidence is that associated with changing the operation of the North Atlantic meridional overturning circulation (MOC). The engine for this circulation is sinking of dense (cold and saline) seawater at high northern latitudes and the brake, by this hypothesis, is the freshening of surface waters by various means, including atmospheric precipitation and melt from glaciers and

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Marc d’Orgeville and W. Richard Peltier

observations. The observed decadal salinity variability along the coast of North America, on the other hand, has not been directly related to the PDO but rather to a distinct Pacific mode of variability ( Di Lorenzo et al. 2008 ). The second goal of this paper will be to demonstrate that salinity plays an active role in the development of the PDO in the simulations presented herein; an explanation of the PDO time scale delivered by the model will be provided based on this extension to the usual analysis

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Guido Vettoretti, Marc d’Orgeville, William R. Peltier, and Marek Stastna

previously from a more “El Niño–like” state (i.e., from an enhanced equatorial Pacific zonal SST gradient during the early Holocene to a weaker gradient during the mid-Holocene). The state of the tropical Pacific during deglaciation remains controversial, with some records showing contradicting results in temperature reconstructions (e.g., Koutavas et al. 2002 ; Kienast et al. 2006 ) along with differences in ocean salinity and precipitation (e.g., see Pahnke et al. 2007 for a summary). Two records

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Stephen D. Griffiths and W. Richard Peltier

buoyancy frequency N are required. For the present-day ocean, N can be estimated from observations. However, this cannot be done for LGM, because data, such as the few estimates of temperature and salinity in the deep ocean given by Adkins et al. (2002) , is too sparse. This is an important issue, because the shallow marginal seas almost entirely disappear at LGM, as shown in Fig. 1 . Thus, D BL provides less drag, so that internal tide drag is thought to play a major role in setting LGM tidal

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J. Paul Spence, Michael Eby, and Andrew J. Weaver

basin (roughly 30 yr; Fanning and Weaver 1997 ). The integration times of the two eddy-permitting models exceed the thermocline adjustment time scale, but are not sufficient to remove all of the long-time-scale transients in the deep ocean. Time step interval data do not show a consistent linear trend in potential temperature, but a weak linear salinity trend of roughly 0.0040 psu per century is evident in the three higher-resolution models. By the end of the control equilibrations, the range of

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