AMELIORATIONS OF PRESENT ARCTIC CLIMATES 401 



the tendency ever present to move toward an equilibrium of salinity 

 and of temperature. 



When the Labrador current encounters the Gulf Stream at the 

 eastern angle of the American continent, formed by Newfoundland, 

 great irregularities and interdigitations of current are developed 

 and its further course becomes obscure. 



c) The surface concentration of salt. — The foregoing warm 

 northward-going and cold southward-going currents receive prac- 

 tically all the fresh waters shed from the adjacent lands. They 

 also receive nearly all of the fresh waters that fall in areas where 

 excess of precipitation over evaporation prevails, and practically 

 all the melt waters of the Arctic ice-floes and icebergs. Taken 

 together, they embrace nearly all of the surface waters that are 

 much subject to dilution. This dilution is the chief reason why they 

 remain surface waters. 



Over against these areas of surface dilution stand the areas in 

 which evaporation exceeds precipitation and the surface waters grow 

 more and more saline. This increasing salinity adds to their density 

 and gives them a tendency to descend, so that, while it is necessary 

 to recognize that, for the time being, they are surface waters, and so 

 in a formal sense part of the upper strata of the Atlantic column, they 

 are really the initial stage of a lower layer composed of more highly 

 saKne and hence denser waters even though they remain warm. 

 The evaporating areas center on "the 30° dry belt," but this belt is 

 crossed by storm tracts near the western border of the Atlantic, 

 chiefly in the gulf region. Nearer the center of the ocean a large 

 area is developed in which descending air prevails rather persistently, 

 and evaporation is notably in excess of precipitation, the Sargasso 

 area. In addition to the Sargasso area in the mid- Atlantic, the 

 Mediterranean region is a marked area of concentration of salt by 

 evaporation. It is the more distinctive because it is isolated from 

 the ocean except for its slender connection through the Straits of 

 Gibraltar. It is a peculiarly instructive type. The saline waters 

 of these two tracts will be further considered in connection with 

 the middle Atlantic layer to which they give rise. 



d) The upwelUng areas. — It is only necessary merely to mention 

 these tracts here for the sake of completeness. They are smaller 



