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PRINCIPLES OF STRATIGRAPHY 



by Krummel for the heat capacity of waters of different saHnity 

 at 17.5° C. (20:27^): 



Salinity in permille . 



15 I 20 



25 



30 I 35 



40 



Heat capacity 1 1 . 000 



0.982 0.9680.9580.951 0.945 



0-9390-932 



0.926 



IVarming of the Water Body. The heat conductivity of water 

 is very low. It has been calculated that a mass of water 5,000 

 meters deep, and of a uniform temperature of 0° C, would, if in 

 contact with a heat source of 30° C. at the surface, experience the 

 following rate of warming, providing no other factor, such as con- 

 vection currents, etc., entered in : In 100 years no appreciable in- 

 crease in temperature would be found at a depth of 100 meters ; in 

 1,000 years not one per cent, of the surface warmth is to be found at 

 a depth of 300 m., while it takes 10,000 years to carry this fraction 

 of the surface warmth to a depth of 1,000 m., and one million years 

 to carry it to a depth of 4.900 m. After 1,000 years the temperature 

 at a depth of 100 m. will be 7.3° C, while at 200 -m. it will be only 

 0.6° C. The temperature of 15° C. descends in a half year 1.3 

 meters, in a year 1.85 m., in 10 years 5.8 m. Thus daily or yearly 

 variation of temperature is of little significance for great depths so 

 far as conductivity of water is concerned. 



Warming of the water is, however, produced by the absorption 

 of the sun's rays, which penetrate to a certain depth, and through 

 vertical convection currents. The latter are in part due to the 

 evaporation on the surface and the consequent increase in density, 

 which brings about a readjustment between the denser surface and 

 the lighter, deeper waters. In the tropical waters of the Indian 

 Ocean the average evaporation during the day is ^4 to 3^ mm. 

 per hour, which, for a surface layer of i mm., with a temperature 

 of 26° C. and a saHnity of 35 permille at the beginning, would re- 

 sult in an increase of 13 to 16 permille at the end of the hour, or 

 an increase in density from 1.023 to 1.033, oi" ^-^2)7^ which would 

 cause this water to sink, carrying with it its temperature of 26°. Of 

 course, the water begins to sink long before it has reached that 

 density, in fact, as soon as it becomes slightly heavier through in- 

 creased salinity. 



Average Surface Temperature. The average temperature of the 

 surface of the oceans varies from — 1.7° C. at the poles to 27.4° C. 

 at 5° N. latitude, the latitude of maximal surface temperature. It 

 varies in the different oceans, where the maximum is 26.83° C. in 

 the Atlantic, 27.88° C. in the Indian, 27.20° C. in the Pacific. In all 



