NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC II5 



produces the observed variations in relation between the surface 

 temperature in the middle of the Atlantic Ocean and that of the 

 east shore. To be sure our observations have been assembled for 

 only the coldest part of the winter. We may assume, however, 

 that the relation of this season holds good for other times of the 

 year. 



We may well suppose the variations in the average height of the 

 water may also be brought about by variations in the velocity of the 

 currents which are not directly caused by the wind, but even if this 

 less probable assumption should be admitted, it is particularly difficult 

 to explain the variations in the observed relation of the surface 

 temperature in the Atlantic Ocean by such variations in the cur- 

 rent velocity. These appear to be naturally explained by the condi- 

 tion of the wind. 



However, it may be urged on the other hand that the precipita- 

 tion over regions draining into the North Sea and the Baltic Sea 

 must be of influence particularly upon the height of the water of 

 the Baltic Sea. But this influence must obviously be ot mmor 

 importance compared with that of the wind. A hindrance of the 

 outflow of water at the portal of the Baltic Sea in consequence of 

 the wind will obviously be of greater influence on the height of 

 the water within than the greatest reasonable increase of the precipi- 

 tation which may be imagined, so long as the outflow is not hin- 

 dered in the Kattegat and in the Belts. 



A hindrance to the outflow of water from the Baltic Sea may 

 be thought of in two ways. The winds can cause a rise of the 

 height of the water in the North Sea at the mouth of the Kattegat 

 or the winds in the Kattegat may hold back the water within the 

 Baltic. In both cases there is to be expected a more or less inter- 

 mittant renewal of the deeper lying waters in the Baltic. 



According to the Swedish investigations (see O. Pettersson, 1894, 

 page 532) there was an inflow of salty water from outside, in the 

 deeper layers of the Gulmar-fjords at the mouth of the Kattegat 

 in the spring and summer in the years 1890 and 1893. In the year 

 1899 the ground water in the Gotland-Mulde in the Baltic was re- 

 newed (see Krummel, 1907, pages 352 to 353). In the beginning 

 of the year 1903 the ground water in Bornholm Deep and in the 

 Danzig-Mulde was renewed. In the autumm of 1905 the ground 

 water in the Gotland-Mulde and in the Danzig-Mulde was renewed 

 and later in the following year in the Bornholm Deep (Krummel, 

 1907, p. 301). 



