Figure 1: A schematic diagram of the Upper Cell and Lower Cell of the global MOC emanating from, respectively, northern and southern polar seas. | Nature Geoscience

Figure 1: A schematic diagram of the Upper Cell and Lower Cell of the global MOC emanating from, respectively, northern and southern polar seas.

From: Closure of the meridional overturning circulation through Southern Ocean upwelling

Figure 1

The zonally averaged oxygen distribution is superimposed, yellows indicating low values and hence older water, and purples indicating high values and hence recently ventilated water. The density surface 27.6 kg m−3 is the rough divide between the two cells (neutral density is plotted). The jagged thin black line indicates roughly the depth of the Mid-Atlantic Ridge and the Scotia Ridge (just downstream of Drake Passage) in the Southern Ocean (see Fig. 2). Low-latitude, wind-driven shallow cells are not indicated. General patterns of air–sea surface density (equivalent buoyancy) flux, B (red or blue indicating that surface waters are being made less or more dense, respectively; broad pattern of zonal surface wind stress, , ⊙: eastward; , westward). Coloured arrows schematically indicate the relative density of water masses: lighter mode and thermocline waters (red), upper deep waters (yellow), deep waters including NADW (green) and bottom waters (blue). Mixing processes associated with topography are indicated by the vertical squiggly arrows. This schematic is a highly simplified representation of a three-dimensional flow illustrated more completely in Box 1.

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