Water North Atlantic Deep

Conventional T-S diagrams for specific locations in the individual oceans are shown in Fig. 10-4. The inflections in the curves reflect the inputs of water from different sources. The linear regions represent mixing intervals between these core sources. For example, in the Atlantic Ocean the curves reflect input from Antarctic Bottom Water (AABW), North Atlantic Deep Water (NADW), Antarctic Intermediate Water (AIW), Mediterranean Water (MW), and Warm Surface Water (WSW). 

A requirement of the heat balance for a steady-state ocean is that the input of new cold abyssal water (Antarctic Bottom Water and North Atlantic Deep Water) sinking in the high-latitude regions must be balanced by input of... 

The conveyor belt is shown schematically in Fig. 10-11. Warm and salty surface currents in the western North Atlantic (e.g., the Gulf Stream) transport heat to the Norwegian-Greenland Seas where it is transferred to the atmosphere. This heat helps moderate the climate of northern Europe. The cooling increases the density resulting in formation of the now cold and salty North Atlantic Deep Water (NADW) (Worthington, 1970). The NADW travels south through the North and South Atlantic and then joins the Circumpolar Current that travels virtually unimpeded in a clockwise direction around the Antarctic Continent. 

Raymo, M. E., Ruddiman, W. F., Backman, J. et al. (1989). Late Pliocene variation in northern hemisphere ice sheets and north Atlantic deep water circulation. Paleoceanography 4,413-446. 

Zhu XK, O Nions RK, Guo Y, Reynolds BC (2000) Secular variation of iron isotopes in north Atlantic Deep Water. Science 287 2000-2002. 

Zachara JM, Kukkadapu RK, Fredrickson JK, Gorby YA, Smith SC (2002) Biomineralization of poorly crystalline Fe(III) oxides by dissimilatory metal reducing bacteria (DMRB). Geomicrobio J 19 179-206 Zhu XK, O Nions RK, Guo YL, Reynolds BC (2000) Secular variation of iron isotopes in North Atlantic deep water. Science 287 2000-2002... 

Abyssal clays are found in greater abundance on the western side of the Atlantic Ocean than on the eastern side. This is due to bottom topography that restricts the flow of North Atlantic Deep Water and Antarctic Bottom Water to the western side of the basin. The lower temperature of the western waters causes the CCD to be somewhat shaUower than on the east side of the basin as calcite solubility increases with decreasing... 

NADW, North Atlantic Deep Water This is a deep water mass formed in the North Atlantic. 

Deep Water Masses AABW Arvtarctic Bottom Water PDW Pacific Deep Water lODW Indian Ocean Deep Water NADW North Atlantic Deep Water... 

North Atlantic Deep Water (NADW), which is formed with an initial 5 C-value between 1.0 and 1.5%c, becomes gradually depleted in C as it travels southward and mixes with Antarctic bottom water, which has an average 8 C-value of 0.3%c (Kroopnick 1985). As this deep water travels to the Pacific Ocean, its C/ C ratio is further reduced by 0.5%o by the continuous flux and oxidation of organic matter in the water column. This is the basis for using 8 C-values as a tracer of paleo-oceanographic changes in deep water circulation (e.g., Curry et al. 1988). 

Reconstructions of pathways of deep-water masses in the North Atlantic during the last 60,000 years have been performed by analyzing high resolution records of benthic foraminifera Cibicides wuellerstorfi as this species best reflects changes in the chemistry of bottom waters (Duplessy et al. 1988 Samtheim et al. 2001). The initial 5 C-signature of North Atlantic Deep Water (NADW) is 1.3-1.5%c. As... 

Elliot M, Labeyrie L, Duplessy JC (2002) Changes in North Atlantic deep-water formation associated with the Dansgaard-Oeschger temperature oscillations (60-10 ka). Quat Sci Rev 21 1153-1165... 

Hernes, R J., and Benner, R. (2006). Sources and fluxes of terrigenous organic matter in the North Atlantic Ocean and North Atlantic Deep Water. Mar. Chem. 100, 66-79. 

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)... 

Figure l.Z( Maps of annual mean nitrate concentrations at (a) surface, (b) on the isopycnal surface (j0 = 26.80 representing Subantarctic Mode Water in the southern hemisphere, and subpolar mode waters in the northern hemisphere, and (c) on the isopycnal surface ff2 37.00 representing North Atlantic Deep Water. Based on data from the World Ocean Atlas 2001 (Conkright et ah, 2002). 

The choice of the 2.3 °C offset in the temperature transformation was predicated on the assumption that the vertical temperature distribution was pinned at the lower end by North Atlantic Deep Water flow. Transforming and rearranging Equations (63) with the definitions in (65) gives... 

Curry W. B. and Oppo D. W. (1997) Synchronous, high-frequency oscillations in tropical sea surface temperatures and North Atlantic deep water production during the last glacial cycle. Paleoceanography 12, 1-14. 

Several decades ago it was realized that chemistry of the shells of benthic foraminifera (carbon isotope and Cd/Ca ratios) carried an imprint of the nutrient content of deep-water masses (Shackleton, 1977 Broecker, 1982 Boyle, 1981). This led rapidly to the recognition that the water masses in the Atlantic Ocean were arrayed differently during the last glacial maximum than they are today, and the hypothesis that the glacial arrangement reflected a diminished contribution of low-nutrient North Atlantic deep water (NADW) (Curry and Lohmann, 1982 Boyle and Keigwin, 1982). More detailed spatial reconstructions indicated a shallow nutrient-depleted water... 

Rutberg R. L., Hemming S. R., and Goldstein S. L. (2000) Reduced North Atlantic deep water flux to the glacial Southern Ocean inferred from neodymium isotope ratios. Nature 405, 935-938. 

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