174 Concluding Remarks 



JUSTIFICATION FOR TREATING THE GULF 

 STREAM SYSTEM AS AN ENTITY 



Perhaps it has occurred to the reader to wonder whether there is any 

 justification for treating the Gulf Stream System as a physical system in 

 any sense separable from the general circulation of the North Atlantic 

 Ocean. If the Gulf Stream were a river of very warm water flowing through 

 a colder environment, there would be little doubt that it should be con- 

 sidered a distinct physical phenomenon. As we have seen in the preceding 

 chapters, the most clear-cut feature of the entire system is that it is really 

 a flow along the very edge of the juncture of a mass of cold water and a 

 mass of warm water. Therefore, one is led to inquire whether the primary 

 physical phenomena to discuss are not the origin and nature of the two 

 contrasting water masses, and whether it is not proper to regard the Gulf 

 Stream current system as merely a secondary feature associated with their 

 zone of contact. 



From a historical point of view, the Gulf Stream has always been the 

 primary feature of interest in the western North Atlantic, and the efforts 

 of the first scientific oceanographic explorations were concentrated on it 

 because it was so clear-cut an entity. 'It' could be crossed in a day; 'its' 

 total water transport could be determined ; ' its ' changes in position could 

 be plotted; 'it' had an edge, a core of high velocity, a countercurrent, and 

 so on. Compared to other regions of the ocean, it seemed one where 

 techniques of measurement, such as the indirect velocity determinations 

 based on the geostrophic approximation, could be made with a reasonable 

 degree of precision. When one considers the vast central oceanic areas, or 

 the eastern sides of oceans, where the current features are very faint and 

 indistinct — almost beyond the reach of standard means of measurement — 

 it is no wonder that oceanographers on the western sides of oceans often 

 consider themselves especially fortunate to possess such strong current 

 systems near their coasts and, as a result, have spent much more time 

 cruising in these strong currents than in obtaining detailed information 

 about the great water masses on either side. 



Also, from the point of view of theoretical studies, the Gulf Stream 

 System has a distinct reaHty of its own. The outstanding feature of these 

 theories (discussed in Chapters VII and VIII) is that the transport solu- 

 tions are independent of any assumptions regarding the density structure. 

 The Gulf Stream would exist, according to these theories, whether it is 

 driven by wind stress or by a thermohaUne process. It would exist whether 

 the ocean were half as deep as it is, or ten times as deep. The velocities 

 would be different, but the pattern of the transport hnes would be the 

 same. The Gulf Stream System emerges from these theories as a boundary 



