WATER MASSES AND CURRENTS OF THE OCEANS 



169 



isotherms generally slope downward toward the south, indicating a 

 flow toward the east, but the slope is not uniform and countercurrents 

 or eddies are present between the east-flowing branches of the current. 

 The detailed work that was conducted by the International Gulf 

 Stream Expedition of 1938 clearly shows the complicated details of the 

 oceanographic conditions. Between June 1 and 22, 1938, the German 

 vessel, the Altair, and the Norwegian vessel, Armauer Hansen, occupied 

 159 stations in an area of less than 100,000 square miles, and at one 

 station the Altair anchored and made hourly observations of temperature, 

 salinity, and currents at a number of depths between the surface and 

 800 m for a period of 90 hours. The dense network of stations showed 



48° N 



Fig. 41. Temperature profiles across the Gulf Stream off Chesapeake Bay and 

 across the North Atlantic Current to the north of the Azores. 



even greater irregularities than one might expect. Thus, at 600 m, 

 the temperature varied between approximately 7° and 13°, and differences 

 up to 5° were observed at distances of less than 40 miles. Some of the 

 observed features may be due to the influence of the bottom topography, 

 and others may be related to traveling disturbances. Regardless of how 

 the features are interpreted, they do show that caution has to be exercised 

 when drawing conclusions from a few scattered observations, because 

 such scattered data maj^ not be representative. They also show that an 

 intensive mixing takes place in mid-ocean. 



Records at stations that were occupied in 1931 by the Atlantis along 

 the mid-Atlantic Ridge in long. 30°W demonstrate that in spite of 

 irregularities one can distinguish between two major branches of the 

 North Atlantic Current. The northern of these branches flows between 

 latitudes 50° and 52°N, at the boundary between the water of the Gulf 

 Stream system and the Subarctic Water, and carries water which repre- 

 sents Gulf Stream water mixed with waters of the Labrador Current. 



