Gulf Stream

Of considerable usefulness in transporting heat toward the poles are the ocean currents. They are particularly effective because of the high heat content of water. Significant poleward-moving currents are the Brazil, Kuro-shio, and Gulf Stream currents. Currents returning cold water toward the equator are the Peru and California currents. 

Theoretical concepts for generating electricity from ocean currents such, as the Gulf Stream, and salinity gradients (differences in salt content) are being investigated. More research and development is required before these concepts reach the stage of demonstration power plants. 

Fig. 1. Major oceanographic features 1. Canary Current, 2. Gulf Stream, 3. North Atlantic Current, 4. Sargasso Sea, 5. North Atlantic Gyre, 6. Labrador Current, 7. Loop Current, 8. North Pacific Gyre, 9. South Equatorial Current, 10. Benguela Current, 11. Humboldt Current, 12. Antilles Current, 13. Florida Current, 14. Brazil Current, 15. Kuroshio, 16. Antarctic West Wind Drift.

The first reports of plastic in the North Atlantic indicated the presence of 50-12,000 particles/km in the Sargasso Sea in 1972 (52) and from 0-14.1 particles per m in coastal waters of southern New England (42), where the main source was river-borne effluents from plastic fabrication plants (44). Plastic objects discarded from boats and from recreational activities on beaches were the main sources of debris in Narragansett Bay, being deposited at a rate of 9.6 g m of beach front per month (53). During a detailed survey off the southeast coast of the United States (43, 54), fragments of plastic were present in about 70% of the samples collected from the waters of the continental shelf, the continental slope and the Gulf Stream between Florida and Cape Cod, 50% of those from the Caribbean Sea, and 60% of those from the Antilles Current. Since unprocessed plastic was more prevalent in continental shelf waters and fabricated objects were common offshore but rare near land, the authors surmised... 

Poleward-flowing, warm, surface, western boundary currents such as the Gulf Stream... 

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. 

The D-O events are far too rapid to be caused by insolation changes, and they most likely result from changes in ocean circulation. Their prominence and clarity in the Greenland cores relative to the Antarctic ones is due to the proximity of Greenland to the sites of deep-water formation in the North Atlantic and the tremendous amount of heat being delivered to them by the Gulf Stream (Broecker and Denton, 1989). 

The second feature of the surface layer is the atmosphere, which we have described already under the discussion of Earth s temperature, but we need to add a note on its flow as it is deeply involved with water circulation. The flow of water vapour due to atmospheric flow, winds, is not independent of the flows of rivers and currents in the sea, e.g. the Gulf Stream. Of course, both are coupled to temperature and its gradients from North to South. In fact, there is intense linked... 

The RGB composite of the coefficients of determination of the individual linear correlation coefficients (Figure 2.26) shows that for the northern hemisphere high correlations of volatilisation rate and wind speed in the Atlantic Ocean can be found in the Gulf Stream and low values in the Labrador Sea and the adjacent Davis Strait. High correlations with the sea surface temperature are located near 45 °N close to the eastern coast of the American continent, in the Baltic Sea, North Sea and in... 

Significant amounts of manganese and phosphorite deposits are present on the top of the Blake Plateau, which lies at the foot of the continental margin off the southeastern United States at depths of 500 to 900 m. The Gulf Stream has eroded most of the unconsolidated sediments at this location, leaving only a carbonate platform, which has become covered with pavements of manganese and phosphorite covering an area of 5000 km ... 

Slowing of meridional overturning circulation in the North Atlantio from 1998 to 2004. Gulf Stream was deflected southward. Deep southerly flows deolined by 50%. 

Surface Water. The volatilization half-life of naphthalene from surface water (1 m deep, water velocity 0.5 m/sec, wind velocity 22.5 m/sec) using experimentally determined Henry s law constants is estimated to be 16 h (Southworth, 1979). The reported half-lives of naphthalene in an oil-contaminated estuarine stream, clean estuarine stream, coastal waters, and in the Gulf stream are 7, 24, 63, and 1,700 d, respectively (Lee, 1977). Mackay and Wolkoff (1973) estimated an evaporation half-life of 2.9 h from a surface water body that is 25 °C and 1 m deep. In a laboratory experiment, the average volatilization half-life of naphthalene in a stirred water vessel (outer dimensions 22 x 10 x 21 cm) at 23 °C and an air flow rate of 0.20 m/sec is 380 min. The half-life was independent of wind velocity or humidity but very dependent upon temperature (Klopffer et al., 1982). 

Each extract was added to two media, both of which were enriched with ES enrichments (18, 21) one made with natural seawater (Florida Gulf Stream Seawater, Carolina Biological Supply Co.) and designated ESNW the other made with artificial seawater (21, 22), and designated ESAW. To prevent precipitation during sterilization, 0.12 g NaHCO and 1.44 mis 1 N HCl were added to each liter of seawater immediately before autoclaving. After autoclaving, when the seawater base was cool, ES enrichments were added aseptlcally. 

Real environmental transport processes contain all these phenomena that we encountered in the dining car. For instance, large ocean currents, such as the Gulf Stream, act as the dining car. Within these currents there are parcels of water called turbulent eddies which move relative to each other. In addition, small plants and animals carried in the current move relative to the surrounding water, take nutrients up, and mix them within their bodies. 

Turbulent flow means that, superimposed on the large-scale flow field (e.g., the Gulf Stream), we find random velocity components along the flow (longitudinal turbulence) as well as perpendicular to the flow (transversal turbulence). The effect of the turbulent velocity component on the transport of a dissolved substance can be described by an expression which has the same form as Fick s first law (Eq. 18-6), where the molecular diffusion coefficient is replaced by the so-called turbulent or eddy diffusion coefficient, E. For instance, for transport along the x-axis ... 

Consequently, the choice of the averaging time s determines which eddies appear in the mean advective transport term and which ones appear in the fluctuating part (and thus are interpreted as turbulence). The scale dependence of turbulent diffusivity is relevant mainly in the case of horizontal diffusion where eddies come in very different sizes, basically from the millimeter scale to the size of the ring structures related to ocean currents like the Gulf Stream, which exceed the hundred-kilometer scale. Horizontal diffusion will be further discussed in Section 22.3 here we first discuss vertical diffusivity where the scale problem is less relevant. 

As mentioned earlier, turbulent motion is usually more intensive along the horizontal than the vertical axis. Turbulent structures (eddies) can be horizontally very large. For instance, the eddies or gyres produced by the Gulf Stream are more than 100 km wide. Thus, for horizontal transport the separation between random and directed motion plays a more crucial role than for the case of vertical diffusion. 

In the North Sea the pipeline surroundings will be at sea bottom temperature, so we are Interested in minimum temperatures at that location. Surprisingly, in the deeper water (250 ) of the northern North Sea areas which are affected by the Gulf Stream, the minimum sea bottom temperatures may be as high as 46 to 48°F. In southern North Sea areas which are less affected by the Gulf Stream and also may be shallower, with bottom temperatures more influenced by wave action, we can expect minimums of 40°F or less. Only in very shallow waters near shore can we expect minimum temperatures approaching 32 F. 

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