1 64 WATER MASSES AND CURRENTS OF THE OCEANS 



(1) The Florida Current, comprising all the northward-moving water 

 from the Straits of Florida to a point off Cape Hatteras, where the current 

 ceases to follow the continental slope. The Florida Current can be traced 

 directly back to the Yucatan Channel, because the greater part of the 

 water flowing through this strait continues on the shortest route to the 

 Straights of Florida and only a small amount sweeps into the Gulf of 

 Mexico, later to join the Florida Current. After passing the Straits 

 of Florida the current is reinforced by the Antilles Current, but the name 

 *^ Florida Current" is retained as far as to Cape Hatteras. 



(2) The Gulf Stream, comprising the mid-section of the system from 

 the region where the current first leaves the continental slope off Cape 

 Hatteras to the region to the east of the Grand Banks in about longitude 

 45°W, where the stream begins to fork. This application of the name 

 "Gulf Stream" represents a restriction of the popular term, but such a 

 restriction is necessary in order to introduce clear definitions. 



(3) The North Atlantic Current, comprising all the easterly and 

 northerly currents of the North Atlantic from the region to the east of the 

 Grand Banks, where the Gulf Stream divides. The branches of the 

 North Atlantic Current are often masked by shallow and variable wind- 

 drift surface movements that have become commonly known as the North 

 Atlantic Drift. 



The terminal branches of the Gulf Stream system are not all well 

 known, but among the major ones are the Irminger Current, which flows 

 toward the west off the south coast of Iceland, and the Norwegian 

 Current, which enters the Norwegian Sea across the Wyville Thomson 

 Ridge and which ultimately can be traced into the Polar Sea. Other more 

 irregular branches turn to the south and terminate in great whirls off the 

 European coast. 



The Florida Current. The energy of the Florida Current appears 

 to be derived directly from the difference in sea level between the Gulf 

 of Mexico and the adjacent Atlantic coast, the observed difference 

 between Cedar Keys and St. Augustine being 19 cm. Assuming that this 

 hydrostatic head accounts for all of the energy, and assuming frictionless 

 flow, Montgomery finds that the velocity through the Straits of Florida 

 should be 193 cm/sec, which is somewhat higher than the average velocity 

 at the center of the current. The difference in level is probably main- 

 tained by the trade winds, and the energy of the Florida Current is therefore 

 derived from the circulation of the atmosphere. 



Within the current flowing through the Straits of Florida the dis- 

 tribution of density must adjust itself in the usual manner so that the 

 lighter water will be found on the right-hand side of the current and the 

 denser water on the left-hand side, and so that the sea surface, instead of 

 coinciding with a level surface, rises toward the right-hand side of the 

 current. Across the Florida Current, this rise amounts to about 45 cm, 



