Chapter III 



Temperature in the Ocean ^ the Three- 

 dimensional Temperature Distribution 

 and its Variation in Time 



1. Heat Sources, Heat Exchange and Heat Budget in the Ocean 



All changes of state in the liquid and gaseous envelopes of the Earth are due basically 

 to energy changes. Energy is very largely supplied from outside the Earth, principally 

 from the sun which provides an inexhaustible source of radiant energy for the Earth. 

 There is a constant inflow of energy from the sun and a constant outgoing radiation 

 from the Earth into space. The Earth does not retain the energy supplied to it but 

 returns all except a vanishingly small part to outer space in the same form (radiation) 

 in which it received it. The possibility of life on the Earth and all changes of state on 

 the Earth depend not so much on the inflow of solar energy as on the enormous supply 

 of entropy involved in the conversion of the high-temperature radiation from the sun 

 to the low-temperature radiation from the Earth. 



These considerations lead to the concept of a stationary state as far as the heat 

 energy of the Earth, taken as a whole, is concerned. This constancy in heat energy can 

 be confirmed for the solid part of the Earth and for the atmosphere, and it can be 

 expected that it holds as a close approximation for the energy budget of the oceans. 

 There are, of course, small variations with time in the temperature of the ocean, but 

 these can be taken as variations around a mean value which remains essentially un- 

 changed . 



Heat budget of the ocean. Tn this quasi-stationary state all the supply in energy is 

 balanced by equally large losses of energy. The most important factors are the radia- 

 tion, the interchange of sensible heat with the atmosphere above the sea and evapora- 

 tion from the surface of the sea or the condensation of atmospheric water vapour. 

 Other minor sources of heat that may be mentioned besides the above stated ones are 

 listed in Table 36. 



The order of magnitude of the heat amounts involved in each of these processes 

 varies considerably. The largest is certainly the heat absorbed from solar and sky 

 radiation which is the principal factor in the heat budget of the very upper layers of the 

 sea. At its upper limit the Earth atmosphere obtains per cm^ by normal incidence an 

 energy of l-94g cal/min (solar constant). The entire surface of the Earth receives 

 per cm^ on the average 0-485 g cal/min or during the entire day 700 g cal/cm^. This 

 incoming radiation from the sun is largely short wave. Its intensity is decreased on 

 passing through the atmosphere so that only 43%, that is 0-21 g cal cm - min"^ 



88 



