Ocean currents

Errors in elemental fluxes derived from crustal estimates are larger than, or similar to, the value of the actual flux estimate for many of the major elements silicon, aluminum, iron, manganese, magnesium, and sodium. The fluxes for these elements are thus poorly constrained, but these estimates do serve as conservative bounds on the fluxes. Unfortunately, these bounds overlap the fluxes derived from hydrothermal fluid data and river data. For this reason, current ocean-crust flux estimates do not provide independent evidence for the magnitude of hydrothermal fluxes in the geochemical cycle for these elements. Within the bounds of these uncertainties, the data indicate that ocean floor hydrothermal processes may balance (or compound ) missing global fluxes of these elements. For these reasons, these elements are not discussed here in any detail. 

Recent estimates indicate that of the approximately 200000 tons of mercury emitted to the atmosphere since 1890, about 95% resides in terrestrial soils, about 3% in the ocean surface waters, and 2% in the atmosphere (Expert Panel on Mercury Atmospheric Processes 1994). Some 20-30% of the current oceanic emissions are from mercury originally mobilized by natural sources (Eitzgerald and Mason 1996). Similarly, a potentially large fraction of terrestrial and vegetative emissions consists of recycled mercury from previously deposited anthropogenic and natural emissions (Expert Panel on Mercury Atmospheric Processes... 

The missing carbon concept arose because radiocarbon-calibrated carbon cycle models predict that the quantity of carbon remaining in the atmosphere after fossU fuel release should exceed that suggested by the direct observation of rising concentrations of carbon dioxide. Three solutions have been proposed. One is that current ocean models cannot be adequately calibrated using radiocarbon. A second is that the biosphere currently acts as a sink for carbon. The third is that the biosphere has been a net source of carbon in the past. 

Every continent on the planet is surrounded by a cleaner, safer, more efficient energy resource. As conventional energy supplies are depleted, means are being developed, and in some cases are in actual operation, to convert the energy found in waves, tidal currents, ocean and river currents, ocean thermal gradients, and offshore wind into usable electric power for utility-scale grids, independent power producers, and the public sector. 

Mapping Ocean Currents. Ocean currents can be at the surface or much deeper. The best known of the... 

Most commercial marine diatomite deposits exploit accumulations resulting from large blooms of diatoms that occurred ia the oceans during the Miocene geological epoch. Diatomite sediments older than the Jurassic period are rare in the fossil record. Commercial deposits of diatomite are accumulations of the fossil skeletons, which can occur in beds as thick as 900 m in some locations (5). Marine deposits must have been formed on the bottom of protected basins or other bodies of quiet water, undisturbed by strong currents, in an environment similar to the existing Santa Barbara Channel or Gulf of California (3,6). 

A number of current coupled ocean-atmosphere climate models predict that the overturning of the North Atlantic may decrease somewhat under a future warmer climate.While this is not a feature that coupled models deal with well, its direct impact on the ocean s sequestration of carbon would be to cause a significant decline in the carbon that is stored in the deep water. This is a positive feedback, as oceanic carbon uptake would decline. Flowever, the expansion of area populated by the productive cool water plankton, and the associated decline... 

The movement of these plates can ies with it continents, ocean basins and mountains. Scientists believe that convection currents are generated as a result of great heat within the earth, as illustrated in Figure 14. lO. Below the crust, the hot rocks and metal in liquid form rise to the crust, cool and sink into the mantle causing a turbulence through heat convection. The hot rocks become hardened at the surface of the mantle and push the crust which is part of the hug plates that are afloat the mantle. This movement of plates can cause the following ... 

In the corrosion protection of marine structures, it is often found that the corrosion rate decreases strongly with increasing depth of water, and protection at these depths can be ignored. Investigations in the Pacific Ocean are often the source of these assumptions [7], However, they do not apply in the North Sea and other sea areas with oil and gas platforms. Figure 16-1 is an example of measurements in the North Sea. It can be seen that flow velocity and with it, oxygen access, is responsible for the level of protection current density. Increased flow velocity raises the transport of oxygen to the uncoated steel surface and therefore determines the... 

New types of anodes have been developed and tested as shown in Fig. 16-5 to improve the possibility of maintenance and repair. They can be lifted onto a ship and repaired. The connecting cables are also replaceable. In shallow water, the anchorage must be accurately calculated because considerable dynamic stressing can occur in heavy seas. The ocean floor must be suitable for long-term anchorage. No supply ships must anchor in the area around the platform. This requirement alone often prevents the installation of impressed current anodes since the operator does not wish or is not able to restrict himself to these conditions. 

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. 

Taylor and Marsh (7) investigated the long-term characteristics of temperature inversions and mixed layers in the lower atmosphere to produce an inversion climatology for the Los Angeles basin. In this area the cooler ocean currents produce an elevated inversion that is nearly always present and traps the pollutants released over the area within a layer seldom deeper than 1200 m and frequently much shallower. 

Enormous amounts of waste dumped into water systems are degrading water quality and causing increased human health problems. In assessing this pollution, there are two distinct problem areas. The first, and worst, is in marine estuaries and associated coastal waters. As fewer and fewer alternatives remain for land disposal, wastes are finding their way more often into water. The second area consists of the oceans themselves, tiltliough it is believed tliat currently not much of a problem exists, because relatively little waste is dumped... 

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