Tides and Currents

FIGURE 10-1. NOAA Ship Ronald H. Brown at Newport, Oregon. Courtesy ofNOAA. 

FIGURE 10-2. Hydrographic Survey Launch off NOAA Ship Pierce, Penobscot Bay, Maine. Courtesy of NOAA. 

Water currents are more difficult to measure than water levels. In the past, observations of currents were made for only a few days at a time 

Current measurements are usually taken by acoustic Doppler meters, which emit an acoustic signal from either a boat or bottom-mounted transmitter. The signal is reflected from sediment or other particles transported by the flow and recorded. The reflected signal is analyzed to detect the Doppler shift in frequency, yielding a measure of flow velocity in three dimensions. 

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Dry environmental quality PetroKlenz must be reconstituted with water and made into a slurry. The organisms will be ineffective if they are applied as dry cultures over the oil. The effective use of PetroKlenz in a biotreatment program is dependent upon the environmental conditions present at the site. Adverse conditions such as cold temperatures, oxygen, nitrogen, or phosphorus-deficient water, chemical toxic load, highly acidic or alkaline conditions, or excessive dilution of biomass by tides and currents, may retard or prevent biodegradation. 

Plankton Plankton are the small organisms that float in lakes and oceans and are moved passively, drifting with the tides and currents. Small plankton are excellent objects for flow cytometric analysis. 

Pinet, Paul R. Invitation to Oceanography. Sudbury, Mass. Jones and Bartlett Publishers, 2000. Includes explanations of the causes and effects of tides and currents, as well as the origins of ocean habitats. 

Cotidal line A line on a chart or map passing through places having the same tidal hour.(The explanations in the footnotes partly were taken from Tide and Current Glossary, Special Publication No. 228, Coast and Geodetic Survey, by Paul Schureman, 1941.)... 

Le Lecheur, E. A., and Sammons, J. C. (1932). Tides and currents in Long Island Sound and Block Island Sound. U. S. Coast Geodetic Surv.. Spec. Publ. 174. 

After a spill, oil spreads across the sea surface as a slick, varying in thickness from micrometers to a centimeter or more. A slick s behavior is a function of the composition of the oil and the prevailing abiotic factors in the area, water temperature, wind, wave action, tides, and currents (Figure 8). 

For the checking measurements conducted by the customer, reflectors were positioned in such away that an optimal view of the dikes was possible from instrument locations. Subsequently the measurements were collected with reference to element-coordinates. Estimates of accuracy concluded that a standard deviation for element-coordinates between 10 and 15mm needed to be adhered to. Due to the incessant motion of the element induced by tides and currents all measurements were carried out on the floating element. 

The models have been calibrated with field observations and the results are given here. Tide and current data from three temporary observation stations are used to verified and validate the present model. By comparison, the numerical calculation results are in good agreement with the measured data (see Fig. 4 and Fig. 5). 

Charles Henry Davis was eommissioned as midshipman in 1823. He served on a frigate until 1828 in the Pacific, and was promoted to lieutenant in 1834. From 1846 to 1849, he worked for the US Coast Survey, discovering a previously unknown shoal that had caused shipwrecks off the coast from New York. He was also responsible for researching tides and currents and acted as inspector for various shipyards. From 1849 to 1855 he was the first superintendent of the American Nautical Almanac Office. 

Once in the ocean, the tides and currents driven by wind control the circulation of shallow water. Seven major currents, shown in Figure 2.1 [27], move water around the globe the West Wind Drift (or the Antarctic Circumpolar Current), East Wind Drift, the North and South Equatorial currents, the Peru Current, the Kuroshio Current, and the Gulf Stream. These currents can move quickly. The Gulf Stream, for example, usually travels at a speed of 3 or 4 knots, which is equivalent to 5.6 to 7.4 kilometers per hour [27]. As these currents spiral through the ocean they form five major gyres the North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean gyres. 

Depending on the local situation (such as bathymetry, tide and currents), only partially loading the vessel and thus reducing the draught might be cost effective. 

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