616 



77?^ Tropospheric Circulation 



66° 



36" 



38» 



740 730 72° 71° 70° 69° 68° 67° 66° 65° 



Fig. 287. Mean temperature (°F) in the upper 200 m layer of the Gulf Stream, 8 June 1950. 



while moving eastwards that large sections of the current can be cut off. This process 

 results in the ejection of a water mass from the current and the formation of large 

 cyclonic vortices on the southern side of the main current. This cut-off process is 

 similar to processes involved in polar jet phenomena in the upper atmosphere which 

 are of major importance in the dynamics of these air currents. The process can be 

 followed clearly in successive charts from 16 June to 21 June. On 17 June this process 

 reaches its maximum stage (Fig. 289). The cyclonic vortex clearly stands out in the 

 band of temperature concentration and in direct current recordings. It was at first a 

 strong vortex but gradually weakened during the following days and finally vanished. 



A further characteristic phenomenon is the break-up of the Gulf Stream into 

 several separate branches. Usually there are three, sometimes separated by counter 

 currents. Figure 290 shows the current velocity and temperature distribution usually 

 found at the sea surface. 



Consideration of these recent results shows that there are three principal questions 

 on the internal dynamics of the Gulf Stream that require an answer. 



(1) Why is the current asymmetrically developed and why is the current core 

 displaced to the left-hand side (looking downstream) ? 



,72° 71° 70° 69° W 68° 67° 66° 65° 



Fig. 288. Position of the Gulf Stream. Mean temperature (°F) of the upper 200 m layer for 

 8 June (full lines) and for 21 and 22 June 1950 (dashed lines). 



