1 86 Density of Water Masses in Ocean, Vertical and Horizontal Density Distribution 



variations of T and S (phase difference of 6 months) it will be at an angle of 135°. 

 For a phase difference of three months the density values will lie either clockwise 

 or anticlockwise around a circle. This method has been used by Neumann (1940) 

 for a close investigation of the annual density variation in the area of the Gulf Stream 

 north of the Azores. Figure 86 shows such annual density variations for some five- 



Sfoo 



340 



332 



West of New Fbundlond 



50°-45''N 



8 10 



45°-50°W 



35-6 



2 13 T 



12 14 16 .18 



50°- 491^ 20°-25''W 



Between New Fcxjndland and Azores 



27-0 26-0 



T' 14 16 



45''-40°N 



20 22 20 



40°-45''W 



14 16 18 20 



45''-40°N 25° 30°W 



Fig. 86. Annual density variation at the surface of the sea in the area of the Gulf Stream 

 north-west of the Azores (according to Neumann). 



degree squares according to the above method. The amplitude is largest {Aa^ = 2-09) 

 at the boundaries of the Gulf Stream and the Labrador Current, then decreases to the 

 east and south-east to only 1-5-1 in o-^. The maximum occurs in late winter (February- 

 March) and the minimum without exception in August. In the western squares the 

 densities lie almost on a straight line inclined at an angle of 135° to the temperature 

 axis. The more or less sinusoidal annual variations in T and S show therefore a phase 

 difference of about six months. 



Similar investigations for other oceanic regions are entirely missing. Bohnecke 

 (1936) has given a chart showing the annual variations in surface density over the 

 entire Atlantic. As may be seen from this chart in the large areas of the North and the 

 South Equatorial Currents the annual variation in ct< is generally less than I-O. It 

 rises locally above 1-5 only at the boundary between the North Equatorial Current 

 and the Equatorial Counter Current (about 10° N.). In the tropics and the subtropics 

 the annual variation is on the whole large only in those areas, where there exists a 

 large annual variation in salinity (mouth of the Amazon, Gulf of Guinea, region with 

 upwelling water east of Cape Verde Island). In higher latitudes the annual density 

 variation remains, in general, also between 1-0 and 1-5, only falling below 1-0 north of 



