Salinity of the Ocean, its Variation in Oceanic Space and in Time 



159 



water from rivers and from precipitation. There is therefore a very close correlation 

 between the two phenomena if one applies a readily explicable phase difference of 

 about two months. Gehrke (1910) has already pointed out that this phase difference 

 becomes smaller and smaller approaching the coast from the open sea. Similar con- 

 ditions are found in the eastern part of the Baltic (Granquist, 1938). 



Of the occasional disturbances in the surface salinity occurring only for very short 

 time due to the influence of external agencies, probably the most interesting is that 

 caused by precipitation. It is to be expected that heavy precipitation of long duration 

 will reduce the salinity. However, this reduction, first affecting the surface, will extend 

 when precipitation continues down to deeper and deeper layers beneath the surface 

 due to turbulent mixing. After the cessation of the precipitation there is a continued 

 equalization of the sahnity change by these turbulent processes that gradually ehmi- 

 nates the disturbances. Some data are found in the literature (Krummel 1907) on 

 the relationship between precipitation and simultaneous and subsequent decreases in 

 salinity, but these observations have been made from moving vessels and therefore 

 do not permit an unequivocal quantitative determination of the effect of dilution 

 by precipitation. Neumann (1940) has given some more recent results on the determina- 

 tion of salinity before, during, and after rain. Figure 66 shows three sets of observation 

 made by the research vessel "Carimare" of the surface salinity given as deviations 

 (l/100%o) of the value at the time of the rain. In total agreement with each other all 

 three cases show minimum salinity at the time and at the end of the rain. After the 

 rain the salinity rose, at first rapidly and then more and more slowly to the value 



-8 -7 -6 -5 -h -3 -2 -1 +1 +2 +3 *h +5 +6 +7 +8 +9 +10 



Fig. 66. Changes in surface salinity due to precipitation (according to the observations of the 

 research vessel "Carimare"). The zero point on the abscissa corresponds to: in case 1 (6-7 

 June, 1938 at 1 7.00 h) ; in case 2 (8 June, 1938 at 04.00 h) ; in case 3(16 June, 1938 at 02.00 h). 



