Atlantic Ocean Basin

One of the more "aesthetically pleasing" relations was put forth for the eastern and western Atlantic Ocean basins by Berger (1977). In his plots (see Figure 4.21) the R0, FL and CCD were generally widely separated and usually close to parallel. The saturation depth (SD) was close to coincident with the R0 level. However, even this picture has problems. If the R0 and SD are closely coincident, how can the 50% dissolution occur that is required to produce the R0 level (Adelseck, 1978) ... 

Figure 4.21. Latitudinal variation of saturation depths (SD) and carbonate sediment facies in the eastern and western Atlantic Ocean basins. (Modified after Berger, 1977.)...

Turekian K.K. (1964) The geochemistry of the Atlantic Ocean basin. Trans, of the New York Acad. Sci. 26,312-330. 

It has been estimated that riverine and atmospheric N inputs in the North Atlantic Ocean basin are at least equal to and may exceed N inputs by biological N2 fixation (Howarth et al., 1996 Paerl and WhitaU, 1999). Therefore, our understanding of marine eutrophication dynamics needs to consider a range of scales including ecosystem, watershed, regional and global. 

North Atlantic Ocean basin, for example, shows the Mid-Atlantie Ridge traveling from north to south across the middle of the basin, with dozens of fracture zones cutting across the ridge from east to west. 

Sediment distribution of surficial materials. North Atlantic Ocean basin. (After Keller, G.H., Shear strength and other physical properties of sediments from some ocean basins. Proceedings of the Conference on Civil Engineering in the Oceans, ASCE Press, San Francisco, CA, 319-417,1968. Reprinted with permission of ASCE.)... 

A schematic distribution of wet unit weight of surficial sediments in the North Atlantic Ocean basin is presented in Figure 8.5 and the North Pacific Ocean basin in Figure 8.6. 

In the Atlantic Ocean basin, the predominant shear strength varies from 3.5 to 7 kPa (Figure 8.44). In the areas of calcareous deposits, the strength increases to 7-10 kPa. Low strengths are associated with small areas along the mid-Atlantic ridge. 

The synthesis of 1 kg of dry plant biomass requires the evapotranspiration of about 300 L of water, although smaller amounts of water are needed by some plants such as desert cacti. Approximately one-third of the annual continental rainfall (100 cm/yr) is returned to the atmosphere by evapotranspiration. Although it accounts for only about 10-15% of global evaporation, plant evapotranspiration can play a major role in local climates. For example, a molecule of water falling on the upper Amazon Basin is recycled on average five times during its eventual return to the Atlantic Ocean. 

Fig. 11-16 Partial pressure of CO2 in surface ocean water along the GEOSECS tracks (a) the Atlantic western basin data obtained between August 1972 and January 1973 (b) the central Pacific data along the 180° meridian from October 1973 to February 1974. The dashed line shows atmospheric CO2 for comparison. The equatorial areas of both oceans release CO2 to the atmosphere, whereas the northern North Atlantic is a strong sink for CO2. (Modified with permission from W. S. Broecker et al. (1979). Fate of fossil fuel carbon dioxide and the global carbon budget, Science 206,409 18, AAAS.)...

Evaporite deposition is a much more episodic process and thus difficult to quantify. Because seawater is significantly undersaturated with respect to common evaporitic minerals, like gypsum and halite, evaporites are only formed when restricted circulation develops in an ocean basin in which evaporation exceeds precipitation. A geologically recent example is the Mediterranean Sea of 5-6 Myr ago. At this time excess evaporation exceeded the supply of ocean water through shallow inlet(s) from the Atlantic Ocean. As salinity increased, first CaS04, then NaCl precipitated. Over time, salt deposits 2-3 km thick formed. This thickness represents about 40 desiccations of the entire... 

Sturm ME, Goldstein SJ, Klein EM, Karson JA, Mnrrell MT (2000) Uranium-series age constraints on lavas from the axial valley of the Mid-Atlantic Ridge, MARK area. Earth Planet Sci Lett 181 61-70 Sun S, McDonongh WF (1989) Chemical and isotopic systematics of ocean basalts implications for mantle composition and processes. In Magmatism in the Ocean Basins. Saunders AD, Norry MJ (eds) Blackwell Scientific Pnbl. Oxford, p 313-345... 

This model was first applied to dissolved oxygen gas (O2) profiles to estimate the rate of aerobic respiration. This biological process is responsible fiar the presence of a pronounced mid-depth O2 concentration minimum in the mid- and low latitudes throughout all the ocean basins. The concentration minimum in the Atlantic can be seen in Figure 4.l4e. The solution to Eq. 4.14, in the presence of an upward vertical advection, is... 

Thus, the Mediterranean Sea must have been refilled in an episodic fashion such that conditions favoring shallow-water evaporite deposition were rapidly reattained. Some geologists have proposed that this was achieved via periodic inflows of seawater from the Atlantic Ocean over the exposed Gibraltar Sill into a nearly dry Mediterranean Sea basin. This must have taken the form of a waterfeU hundreds of meters in height The episodic nature of this process is reflected in the repeating evaporite sequences foimd throughout the Messinian deposits. 

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... 

Atlantic Ocean does not include Mediterranean and Black Sea drainage basins. 

Delaygue et al. (2000) have modeled the present day 0 distribution in the Atlantic and Pacific Ocean and its relationship with salinity (see Fig. 3.19). A good agreement is found between observed and simulated 5 0-values using an oceanic circulation model. As shown in Fig. 3.19 the Atlantic Ocean is enriched by more than 0.5%c relative to the Pacific Ocean, but both ocean basins show the same general patterns with high 0-values in the subtropics and lower values at high latitudes. 

Fecal Bacteria (coliform, FC streptococcal, FS). During the study period, decreases in FC and FS were widespread. Major decreases were particularly evident in parts of the Gulf Coast, central Mississippi, and Columbia basins significant decreases were also noted in the Arkansas-Red basin and along the Atlantic Ocean. During the study period, major efforts were made to control both municipal and agricultural sources of fecal bacteria. 

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