128 The Three-dimensional Temperature Distribution and its Variation in Time 



more recent calculations from the observations made in this trench there is no in- 

 stability in the deepest layers as was previously supposed. Table 55 presents the data 

 obtained in this case. 



Table 55. Vertical temperature distribution in the Philippine Trench: ""Will. Snellius" 

 Exp., Stat. 262 (9° 40-5' N., 126° 50-5' E.) 



* Minimum; j Maximum 



Between 3500 and 10,035 m with almost constant salinity there is an increase in 

 temperature from 1-58 to 2-47°C, an increase of 0-89°C; this increase is, however, 

 less than the adiabatic one ; the stratification is thus still stable but very close to the in- 

 different equilibrium. At a level of 5500 m there exists a small anomaly because a 

 thin layer of water, with a warmer potential temperature (1-26°C), is situated under- 

 neath another layer with a colder potential temperature (1-25°C). The difference is, 

 however, only small. The stratification here is thus very close to a vertically unstable 

 state. However, if the salinity would decrease only a little more with depth the weakly 

 stable temperature stratification could be changed by the salinity into an indifferent 

 or even into a slightly unstable one. 



It was at first supposed that the almost adiabatic or slightly superadiabatic tempera- 

 ture gradient, in the deep-sea trenches and the deep troughs of the major oceans, was 

 due to a heat gain from the solid Earth. The heat transferred from the interior of the 

 Earth to the lowermost water layer per second is 



Q = -2-1 X 10-«gcal/cm2 (see p. 88). 



This heat amount would accumulate in the layer very close to the sea bottom, until 

 such a temperature gradient is formed that the incoming heat per unit time would 

 equalize the heat transfer to the layers above. If the water mass were to be completely 

 motionless, then according to the calculations of Schmidt (1925), the stationary 

 temperature gradient would be determined by the heat entering the layer from the 

 Earth and by the coefficient of thermal conductivity, so that in this case there would be 

 a temperature decrease away from the bottom of 1-5°C in 10 m. 



dO 2-1 X 10-« , ^ ,^3 _, 



-, = y-. :r,r-„ == 1-5 X 10-=^ °C/cm. 



dz 1-4 X 10-^ 



Thus, in a deep-sea trench below 5000 m the temperature should rise linearly due to 

 the heat transferred from the Earth to the water, and at the bottom (10,000 m) would 

 be over 700°C. Since this does not occur it must be concluded that even the deepest 



