Hydrography of the Stream 61 



this type of strategy. So far as the object of exploration is a broad, coarse, 

 climatological-mean picture, these premeditated cruises are successful. 



The bathythermograph introduced a new strategy into the game. Its 

 great value hes perhaps less in the continuous nature of its trace with 

 depth than in the fact that it can be used from a ship under way and that 

 the data obtained from it are quickly and easily interpreted. The oceano- 

 grapher studying the Gulf Stream nowadays keeps a running plot of all 

 bathythermograph information as it comes in. On the basis of his inter- 

 pretation of this information he frequently alters the course of the ship 

 to explore whatever feature he is particularly interested in. The result is 

 that he directs the ship in a series of traverses which he hopes will cross 

 the Stream again and again, in order to obtain a three-dimensional image 

 of its thermal structure and currents. This new strategy has endless 

 possibilities and ramifications, only a few of which have been explored. 

 For example, the chief tactic has been to follow the Stream by a series of 

 zigzag legs. Fig. 28 shows the positions of the Stream as determined by 

 such zigzag bathythermograph cruises during the period 1946-1950, ac- 

 cording to Fuglister and Worthington (1951, fig. 4). 



More than a single ship may be employed to advantage in this type of 

 operation: the Multiple Ship Survey of 1950 employed the zigzag tactic 

 and was able to delineate for the first time a meander pattern showing 

 several distinct waves and an eddy breaking off. The expense and effort 

 involved in portraying this picture were considerable. 



Another type of strategy was developed during the short 1952 cruise of 

 the Bear and Caryn; one ship was employed to make the rapid bathy- 

 thermograph traverses of the Stream, and the other was used in making 

 the slow hydrographic stations and velocity measurements. In this way 

 it was possible to keep a constant check on the position of the slower vessel 

 relative to the chief thermal features of the Stream. This strategy requires 

 at least two ships, one of which should be capable of reasonable speed ; 

 they should never be farther apart than a few hundred miles, otherwise the 

 cruise loses the effectiveness of the multiple-ship type of operation. Even 

 two ships face a formidable situation if the ocean feature under obser- 

 vation is changing rapidly. The 1952 Bear-Caryn cruise is an example. 

 The evidence of six crossings of the Stream showed that the ships were 

 working on the crest of a meander in which the deep velocity and thermal 

 fields were essentially stationary during the six days spent in the area. The 

 surface salinities, as indicated by a recording conductometric cell, were 

 apparently changing rapidly with time, in the course of a widespread in- 

 vasion of freshened water from coastal areas (Chesapeake Bay, Delaware 

 Bay, and Hudson River) which was spreading along and across the Stream. 

 The surface salinities plotted in the course of the cruise cannot, therefore, 



