54 



THE HEAT BUDGET OF THE OCEANS 



increased and will be of particular importance in high latitudes. The 

 amount of radiation which under stated conditions penetrates the sea 

 surface is obtained by subtracting the reflection loss from the total 

 incoming radiation. 



Absorption of Radiation Energy in the Sea. The radiation that 

 penetrates the surface is absorbed in the sea water. The amounts 

 absorbed within given layers of water can be derived by measuring with a 

 thermopile the energies that reach different depths or by computing these 



12 13 14 \5 

 WAVE LENGTH 



19 20 21 22 23 24 >i 



Fig. 8. Schematic representation of the energy spectrum of the radiation from 

 the sun and the sky which penetrates the sea surface, and of the energy spectra in 

 pure water at depths of 0.1, 1, 10, and 100 m. Inset: Percentages of total energy and 

 of energy in the visible part of the spectrum reaching different depths. 



energies by means of known extinction coefficients. Direct measure- 

 ments of energy have been made in Mediterranean waters by Vercelli, but 

 extinction coefficients of radiation of different wave lengths have been 

 determined in many areas (p. 30). For computation of the energy which 

 reaches a given depth it is necessary to know the intensity of the radiation 

 at different wave lengths — that is, the energy spectrum. The reduction 

 in intensity has to be calculated for each wave length, and the total energy 

 reaching a given depth has to be determined from the energy spectrum by 

 means of integration. The definition of the extinction coefficient for total 

 energy corresponds to the definition of extinction coefficients at given 

 wave lengths (p. 27). 



The spectrum of the energy that penetrates the sea surface is repre- 

 sented approximately by the upper curve in fig. 8, which also shows the 

 energy spectra at different depths in pure water. The total energy at any 

 given depth is proportional to the area enclosed between the base line and 



