Ocean circulation Deep Water flow

The abyssal circulation model of Stommel (1958) (Fig. 9-11) predicted that the deep waters flow most intensely along the western boundaries in all oceans and gradually mix into the interior during this flow. 

NADW flows southward the ongoing oxidation of organic matter results in a progressive C-depletion down to less than 0.4%c in the Southern Ocean. Reductions in observed in many cores from the North-Atlantic (Samtheim et al. 2001 Elliot et al. 2002) have been interpreted as meltwater input to the surface ocean (Heinrich events), which caused changes in deep water circulation. 

The distribution of chemical components within the ocean is determined by both transportation and transformation processes. A brief outline of oceanic circulation is necessary to ascertain the relative influences. Two main flow systems must be considered. Surface circulation is established by tides and the prevailing wind patterns and deep circulation is determined by gravitational forces. Both are modified by Coriolis force, the acceleration due to the earth s rotation. It acts to deflect moving fluids i.e., both air and water) to the right in the northern hemisphere and to the left in the southern hemisphere. The magnitude of the effect is a function of latitude, being nil at the equator and increasing poleward. 

The density of the water controls the deepwater circulation. If the density of a water body increases, it has a tendency to sink. Subsequently, it will spread out over a horizon of uniform circulatory system is also known as thermohaline circulation. As shown in Figure 5 of the ocean conveyor belt, the densest oceanic waters are formed in Polar Regions due to the relatively low temperatures and the salinity increase that results from ice formation. Antarctic Bottom Water (ABW) is generated in the Weddell Sea and flows northward into the South Atlantic. North Atlantic Deep Water (NADW)... 

Fig. 6.28 Global oceanic deep-water circulation. Major flow routes are marked by stippled ornament. Deep mixing in the North Pacific is prevented by the topography of the seabed around the Aleutian Arc. Modified from Stommel (1958), with permission from Elsevier Science.

The concentration of dissolved nutrients in the deep waters of the Eastern Mediterranean is much lower than those in other oceans of the world, and when these are mixed into the surface waters they support very low primary productivity. The basic reason for this ultra-oligotrophic status is that the Mediterranean has an anti-estuarine (reverse thermohaline) circulation in which nutrient-depleted surface waters flow into the western basin at the Straits of Gibraltar and then on into the eastern basin at the Straits of Sicily. The deeper counter current consists of Levantine Intermediate Water (LIW) which contains a significant amount of dissolved nutrients. 

Mangini et al. (1982) also established that there had been a marked increase in deep circulation in the Pacific at 70 ka corresponding to the end of interglacial cycle stage 5 based on Th and Pa dating in 9 out of 13 sediment cores from the C-C F.Z. and in all 4 cores from the Aitutaki Passage. These results supported the idea that the onset of glacial events increased ocean bottom water flow in the C-C F.Z.,... 

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