26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. JO 



the years of observation. It is also apparent that the mean tempera- 

 ture of the air in the two other regions, the easterly and the westerly, 

 in the third decade, that is from February 23 to March 4, is higher 

 than would be expected. This feature may be recognized by the 

 consideration of the curves for the whole Atlantic Ocean and most 

 plainly appears in figure 11 (W, L and W-L) from the horizontal 

 march of the curves for the time from March i to 20. 



IV. EARLIER INVESTIGATIONS OF THE TEMPERATURE 

 VARIATIONS OF THE ATLANTIC OCEAN 



It has long since been recognized what a decisive thermal influ- 

 ence the so-called Gulf Stream has on the temperature behavior of 

 the North Atlantic Ocean as well as on the climate of the west 

 and northwest Europe. Hence it was apparent that a change in 

 this ocean current would be of importance on the temperature of 

 the Northeast Atlantic Ocean and the climatological relations of 

 western Europe. 



Prof. Otto Pettersson, in his well-known book on the relations 

 between hydrographic and meteorological phenomena, (1896) made 

 the first important investigations in order to determine the exact 

 relation between the variations of the temperature of the ocean 

 and the relations of air temperature and climate of Scandinavia 

 and north Europe. 



In the lack of continuous temperature measurements of the 

 water-masses of the Gulf Stream itself, he took as the starting 

 point of his investigation the temperature of the ocean at the sur- 

 face near the lighthouses Utsire, Helliso and Ona on the Norwegian 

 coast, where observations for a long period of years were avail- 

 able. In this he assumed that the variations in the temperature 

 of the coast water depended directly on changes in the water-masses 

 of the Gulf Stream which, now cooler, now warmer, are driven 

 upon the coast. This assumption is. however, as we shall show later, 

 not correct. The coast water in which these temperature measure- 

 ments at the lighthouses were made is far different from the water 

 that the Gulf Stream brings. As will later be shown, the surface 

 temperatures, for example at Ona lighthouse, particularly in the 

 winter months of January and February which Pettersson employed, 

 depend completely on the relations of the winds along the coast 

 which naturally also affect the wind relations to the temperature 

 of Scandinavia, so that by this common influence a dependence 

 between the two is brought about. As we shall see later, these 



