FIGURE 4 POSITIONS OF FRONTS WITH RESPECT TO THE OBSERVATION POINT (52° 48 N, 

 35° 30' W)-I230E, 22 SEPTEMBER 1954 



Internal waves with long periods and moderate amplitudes are shown in 

 Figure 2. The temperature values, plotted every 2 hours for 2 days, were 

 taken from BT's of station CHARLIE. The upper solid line in the figure 

 represents the interface between the mixed layer and the thermocline; the 

 lower solid line is the bottom of the thermocline; and the broken lines 

 are isotherms of ^5°, kj , and ky° F. Numbers within the figure indicate 

 solitary temperature values at various levels. 



The period of the waves at the top and bottom of the thermocline is 

 about 6 hours; however, the amplitude of osc ill ation is usually larger at 

 the bottom. Both wave systems appear to be quite independent: they may 

 or may not be in phase. The temperature gradient in the thermocline is 

 not constant but varies continually, sometimes slowly, sometimes rapidly, 

 according to the phase or amplitude relationship of the internal-wave 

 systems at the top and bottom of the thermocline. 



Large amplitude internal waves at the bottom of the thermocline are 

 shown in Figure 5« The interface between the mixed layer and the thermo- 

 cline is shown by the solid line. Temperature values in the interface 



