Density of seawater at the surface of the open sea ranges from 

 about 1.021 to 1.027 g/cm3. Generally about 1.025 g/cm^, density 

 increases with increasing salinity and continually decreases with 

 increasing temperature, provided the salinity is greater than 24.7 o/oo. 

 For lower salinities there is a temperature of maximum density as for 

 pure water. A small increase of density occurs with increase in pressure, 

 which is important because of high pressures in the deep ocean. 



Seawater exhibits the unique properties of solutions, namely, 

 osmotic pressure, depression of freezing point, elevation of boiling 

 point, and reduction of vapor pressure. The observed freezing point 

 is -1.910°C for a salinity of 35 °/oo, the freezing point depression 

 being less than that computed on a basis of complete ionic dissociation 

 by a factor of 0.89. For all practical purposes, the latent heat of 

 evaporation may be taken as that of pure water. 



Specific heat at constant pressure Cp is close to 1 cal/g°C and 

 increases with increasing pressure. The ratio of specific heat at 

 constant pressure to that at constant volume increases with temperature 

 and pressure. Seawater is compressible, and effects of adiabatic pro- 

 cesses, although small, must be taken into account when studying the 

 vertical distribution of temperature in the great depths of the oceans. 

 Adiabatic processes are those that take place without the flow of heat 

 into or out of the volume of the medium under consideration. When a 

 sample of water is brought in an insulated sampling bottle from an 

 initial depth (pressure) to the surface, a certain amount of thermo- 

 dynamic cooling occurs because of the change in pressure, irrespective 

 of the temperature of the local environment. The temperature that the 

 sample would have when brought from the initial depth to the surface 

 without heat flow is called the "potential temperature." 



In the ocean, the important mechanical mixing property is eddy 

 viscosity, which is the effective viscosity occurring on a macroscopic 

 scale in large bodies of fluid. This concept is to be differentiated 

 from molecular viscosity, which is measured on a small sample of fluid 

 in the laboratory. Dynamic viscosity is defined as the ratio of 

 shearing stress to the resulting velocity gradient and expressed in 

 grams per centimeter per second. It is common in -fluid mechanics to 

 use kinematic viscosity, which is dynamic viscosity divided by density 

 and expressed in square centimeters per second. The molecular viscosity 

 for water is about 0.019 cm2/s at 0°C and approximately half this at 

 20°C; the eddy viscosity is substantially larger and may range from 2 to 

 7,500 cm2/s depending upon conditions. Surface tension controls the 

 capillary waves from which larger surface waves receive energy from the 

 wind. The surface tension value is about 76 dyn/cm at 0°C and 73 dyn/cm 

 at 20°C. 



c. Optical and Radio Properties 



Reduction of the intensity of optical radiation in the sea is 

 of major biological interest. In general, light is confined to the 



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