92 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. yo 



VI. VARIATIONS IN INDIVIDUAL FIELDS IN CONSEQUENCE OF 

 THE WATER TRANSFERENCE THROUGH THE REGIONS 



Among the possible causes of the variations in the temperatures of 

 the ocean we will first investigate how far it is likely that the ob- 

 served variations in the surface temperature of the different fields 

 depend upon changes in the quantity of heat available in the water. 

 We may suppose that these changes depend in part upon direct 

 variations in the velocity and volume of the Gulf Stream (off Florida 

 Stream) and the Antilles current which also alter the temperature 

 of it and partly indirectly upon variations of the velocity and vol- 

 ume of the cold Labrador current which may influence its tempera- 

 ture and thereby the temperature of the Gulf Stream, since these 

 cold water-masses must mix therewith. 



THE LOW SURFACE TEMPERATURES IN THE YEARS I903 AND I( 



In order to approach this difficult question it appears simplest to 

 follow the great features of the variations and for this purpose the 

 most striking one to consider first is the great minimum of the year 

 1904. As already said this minimum shows least in the most easterly 

 fields and increases strongly towards the west. This increase can 

 most probably depend upon the fact that the isotherms in the western 

 region are closer together. One might think that it would thereby 

 occur that in the west they should be nearer the middle action point 

 from which the depression goes out. This supposition is apparently 

 strengthened by the fact that the minimum towards 40° west longi- 

 tude and from there to 50° west longitude and more is found not 

 only in 1904 but partially in 1903 also. This is observed in our 

 February curves but is more marked in the March-April curves (see 

 figs. 16 to 18). 



Since the " cold wedge " projects in the region 48° to 50° west 

 longitude from the Labrador current towards the south into the 

 water-masses of the Gulf Stream (see figs. 5 and 6) the conclusion 

 may apparently be drawn that the region between 40° and 50° west 

 longitude is the action center for our minimum. Here perhaps it 

 was first generated in this way that the Labrador Stream in Febru- 

 ary, 1903, and yet more in March, 1903, transported uncommonly 

 cold water southward and the water-masses at the Gulf Stream were 

 thereby cooled. From here the cold water was gradually diffused 

 toward the east over the ocean in the course of the year 1903 and, 

 since the addition of cold water from the Labrador Stream in- 

 creased, it produced a powerful influence over the whole Atlantic 



