FIGURE 14.10. Simplified global NADW cell that only sinks somewhere near the North Atlantic and rises only in the Indian and Pacific Oceans. See the text for usefulness and also problems with this popularization of global circulation, which does not involve processes in the Southern Ocean. Smethie, W. M. and Fine, R. A.: Rates of North Atlantic Deep Water formation calculated from chlorofluorocarbon inventories, Deep-Sea Res., 48, 189–215, 2001. The flow of water along a slope, either on the ground surface or in a series of channels (12.2) Rhein, M., Kieke, D., Huttl-Kabus, S., Roessler, A., Mertens, C., Meissner, R., Klein, B., Boning, C. W., and Yashayaev, I.: Deep water formation, the subpolar gyre, and the meridional overturning circulation in the subpolar North Atlantic, Deep-Sea Res., 58, 1819–1832, 2011. 9. Where does the densest water in the Northern Hemisphere form? In the conveyor belt model of the thermohaline circulation of the world`s oceans, the sinking of the NADW pulls water north from the North Atlantic. However, this is almost certainly an oversimplification of the actual relationship between NADW formation and the strength of the Gulf Stream and North Atlantic drift. [4] Historically, the closure of the Central American isthmus has led to an increase in salinity in the North Atlantic and even an increase in NADW and AABW production.
This trend led to nutrient differentiation between water bodies and may have led to shallower pycnocolin, facilitating the buoyancy of nutrient-rich water. This new circulation was a prerequisite for the long-term increase in upwelling recorded from the late Miocene to the most recent Pliocene sediments (Flohn, 1983). Labrador seawater forms in the western Labrador Sea by convection up to about 1500-2000 metres in late winter. This forms a relatively homogeneous body of water in the Labrador Sea. In recent years, much attention has been paid to the formation of LSW and its changing properties (temperature change from 3.5 ° C to about 2.9 ° C on decadal time scales). Labrador seawater spreads into the North Atlantic, filling both the subpolar vortex and the subtropical vortex. In the subpolar vortex, it is characterized by a minimum of salinity in the vertical. In subpolar and subtropical vortices, it is characterized by a maximum of oxygen in the vertical.
Within both vertebrae, it is also characterized by maximum thickness resulting from its convective source. (Instead of thickness, the size that is often mapped is called potential vorticity, which we haven`t covered in this class. The potential vorticity is inversely proportional to the thickness of the layer and proportional to the Coriolis parameter; PV is retained after flow, essentially as angular momentum, while thickness is not preserved.) (Illustrations by McCartney and Talley, 1982; Lazier, 1993; Talley and McCartney, 1982; Lavender et al., 2000.) The Mediterranean is a concentration basin: evaporation is greater than the supply of fresh water by precipitation and runoff; The water of the Atlantic (AW) that enters the basin through the Strait of Gibraltar compensates for the imbalance. The input of AW, coupled with the flow of saltier intermediate waters, keeps the total salinity almost constant. When it enters the basin (Figure 13.2), AW becomes saltier and cooler. Driven by the loss of buoyancy at the surface, AW sinks to form intermediate water during convective events. Intermediate water formation occurs mainly in cyclonic eddies, favored by reduced stratification in their core, and mainly in the Rhodes gyre, where Levantine intermediate water (LIW) is formed. With regard to the circulation of the eastern tropical Atlantic, emphasis was placed on the exchange of waters between the North and South Atlantic, indicated by the structure of the characteristics. The high temperature and salinity observed in the North Atlantic (NADW) and the propagation have two sources. Most significant is the mixing that takes place at Icelandic-Scottish thresholds between the upper layers of the North Atlantic, overflowing the very dense waters of the Norwegian Sea (Reid, 1996). The other comes from the Mediterranean flow of hot and salt water and acts directly in the upper part of the salt layer up to about 2,500 m. It extends both north into the subarctic gyre and westward across the Atlantic, turning south along the western border.
Thus, the most obvious contribution of the Atlantic to the rest of the global ocean is the layer of warm, salty water that flows south across the South Atlantic and meets the Antarctic Circumpolar Current. The effect of this warm, saline layer is to contribute to the salinity of other oceans and promote the formation of the bottom water of the Weddel Sea. Water from the South Atlantic crosses the equator at all depths to the north. But the warm, saline NADW of the North Atlantic invades low-salinity circumpolar waters from the south, dividing them into two layers: upper and lower CDW. These are three layers, two from the south, one from the north, and it has been assumed that each layer fills its depth range from west to east. The northward flow at the bottom of the cooler, lower salinity from the south corresponds to the AABW, although some of it does not come from below. Penetrations to the north can be seen in phosphate, which is almost the mirror image of oxygen.