480 S. S. VISIIKK SALINITY AS CAUSE OK CLIMATIC CONTRASTS 



present salinity of 3.5 per cent would lielp produce zonal and seasonal 

 extremes chiefly in three ways : 



Increased, salinity reduces the rate of evaporation. According to the 

 experiments of Mazelle and Okada, as reported l)y Kriimmel, evai)orati()n 

 from ordinary sea-water takes place from !) to 30 per cent less rapidly 

 thaii from fresh water, under similar conditions. (The difference in the 

 percental effect of salinity depends largely on whether the water is stirred 

 hy winds or not.) Hence increased salinity during geologic time has 

 reduced evaporation, and thus, doubtless-, has lessened the amount of 

 water vapor in the air. The water vapor in the air is the chief blanketing 

 agent. Eeduction in the blanketing effect of the atmosphere means more 

 severe diurnal and seasonal range of temperature and greater contrast 

 from- zone to zone. 



Salinity lowers the freezing Point 



Increased salinity also means a lower freezing temperature of the 

 ocean. The present salinity of about 3.5 per cent lowers the freezing 

 point of the ocean from 32 degrees Fahrenheit almost to 28 degrees 

 Fahrenheit. If the ocean w^ere fresh and our winters as cold as now, all 

 the harbors of New England and the Middle Atlantic States frequently 

 would be icebound. The North Sea would also be frozen frequently and 

 the British Isles occasionally locked in ice, and in subpolar latitudes tlie 

 area of permanently frozen oceans would be much enlarged. The indirect 

 effects of the lower freezing point of saline than of fresh water are even 

 more significant than the direct effects. 



One direct effect of the low freezing point of saline water is that the 

 open ocean in high latitudes is now cooled below 32 degrees Fahrenheit 

 in winter. Indeed, the temperature of the entire ocean is probably dis- 

 tinctly lower now than it would be if the ocean were less saline. This is 

 because an unfrozen sea loses its heat to the air fairly rapidly, while one 

 covered with widespread ice-floes in high latitudes loses heat much more 

 slowly, for ice is an excellent non-conductor of heat. If the ocean were 

 much fresher than now and the climate as cold, ice-floes would be much 

 more widespread than now. Widespread climatic consequences seemingly 

 result from the lower ocean temperature induced by the free radiation of 

 heat from the open water to the cold air above. Since a liquid's capacity 

 for holding gas in solution varies inversely as the temperature, the ocean 

 is able to absorb and hold considerably more atmospheric C^Oo now than it 

 could if it were not so cold. Certain data suggest that if the ocean were 

 warmed to an average of only 2 degrees Falirenheit above its present 



