Internal Waves 



543 



and of the iso-halines from 35 65 to 37 00°/oo- Lunar period has also been 

 entered; the correlation between the two is clearly recognizable.* 



Table 92 shows the mean vertical oscillation (difference between the extreme 

 positions) for individual isothermes and iso-halines. The amplitude of the 

 vertical displacement is greatest at about 100 m, i.e. where the density 

 gradient reaches its maximum. Upwards and downwards the amplitude is 

 dampened. The lowest position occurs at the time of the upper culmination of 

 the moon in Greenwich. The correct harmonical analysis of the semi-diurnal 

 lunar tide of the 24° isotherm gives as its amplitude 121m and the phase 

 0-24 h lunar time in Greenwich. A glance at Figs. 224 and 225 shows that 

 only the semi-diurnal waves have here any significance. 



The results of the analysis of the current measurements are given in Table 93. 

 The conditions are fairly simple in the case of the semi-diurnal tide. The 



Table 92. Anchor Station "Meteor" 385 (\6°4S-3'N., 

 46°\7VW., depth 2900 m). Mean vertical variation of iso- 

 thermes and iso,halines (Five semi-diurnal lunar periods) 



phase of the upper layer which extends to the depth of the maximum vert- 

 ical displacement (maximum density gradient in about 90 m) is 6-6 h, the 

 phase of the lower layer up to 500 m is about 106 h. The difference 

 between the phases is here 4 h, which should be 6 h in the case when only 

 a semi-diurnal internal tide wave and no other internal waves, and no 

 normal current at the surface tide were present. The mean velocity of 

 the upper layer is 8-4 cm, of the lower layer 9 cm/sec. The decrease of the 

 amplitude for the semi-diurnal tidal current to the small value of 4-4 cm/sec 

 in a depth of 100 m, is quite characteristic. This depth is in the immediate 



* It is of interest that the salinity is not constant in the core of the subtropical under-current 

 with high salinity. During the time the station lasted it increased from 36-9°/ 00 in the beginning 

 to over 37°/ 00 at the end. A definite salinity content is therefore not strictly representative for a de- 

 finite depth or for an individual water particle during the full duration of the observations and 

 consequently, advection processes must have been of certain importance during this time. 



