excitation purity. In coastal regions the water contains many colored 

 absorbers, both inside the bodies of transparent plankters, and as 

 solutes of tannins, chromatins, carotenoids, chlorophyll, and many other 

 "foreign" compounds. In addition, suspended oarticles of very fine mud 

 scatter the light selectively and add to its color. As a result, the 

 transparency of the water is much decreased, and the dominant wavelength 

 shifts through green into the yellow (at 5700 A ) or even into brown. 



The distinctive color of water is a familiar observation and leads to 

 such names as the Black Sea, the Red Sea, the V/hite Sea, the Azure Sea, 

 and the Vermillion Sea. Although water color was used by the earliest 

 navigators to locate familiar water masses and associated current systems, 

 modern navigators depend on more "scientific" (i.e., less natural) methods, 

 For the most part, oceanoqraphers rely on the temperature and salinity of 

 the water and more particularly on their correlation to identify water 

 masses of different origin. Water color is used only as a measure of 

 biological activity, past and present. For example, Steemann-N iel sen 

 found that "the distribution of water color in the open ocean outside 

 influence of land must be closely similar to the quantitative distribution 

 of plankton algae." fr»9' 



In air reconnaissance of the ocean, temperature is the only parameter 

 that currently serves as a discriminant of water masses. Thus it is easy 

 to distinguish the Gulf Stream water from the adjacent slope water by its 

 temperature contrast. But for more subtle differences, this will hardly 

 suffice. Surface temperature is ouickly altered by air temperature and by 

 radiation, so that water masses having very different histories can have 



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