Hydrographic data (at 39° 20' N, 50° 50' W) taken from 

 figure 7 of Fjeldstad (1933) give the following values: 



1 dp o 



— - as 2x 10' 



p dz 



below the permanent thermocline at 1300 meters and 



1 dp « 

 --^Mx 10" 4 

 p dz 



o 



in a rather weak permanent thermocline at 700 meters. 

 Using these values in the equation and taking the ratio of 

 specific energies, we have 



(a ) 3 

 30 7 n 



(a 13 ) a 

 13 n 



approximately , where a and a „ are the amplitudes of 



7 n 13 n 



the nth modes at 700 and 1300 meters respectively. Thus, 

 if displacements inside the permanent thermocline are 

 smaller by an order of magnitude than those outside, the 

 energies are still about the same. Evidently more energy 

 is transmitted horizontally in the frequency channel be- 

 cause a wider band of frequencies is progressing there. 



Breaking of Internal Waves 



Internal waves travel horizontally, and some of 

 them must finally contact bottom near shore. That they 

 reflect, is a mathematical possibility, but not yet a matter 

 of observation. Directions found by observation in very 

 shallow water do not indicate any reflection from shore. 

 All the energy transmitted by internal waves can end as 

 heat, but if it is assumed for the moment that some goes 

 into potential energy, density surfaces would be driven 



