lowing the sloping density surfaces like Neu- 

 mann's (1952) "gliding Austauseh. " 



MIXING VOLUMES 



According to the described process, Gulf 

 Stream water moves through the interaction 

 system from the surface layer to deeper levels 

 after attaining higher density through mixing. 

 This hypothesis requires mixing of a substan- 

 tial amount of slope water into the returning 

 mass. Along transect 1, the ratio of Gulf 

 Stream water to slope water in the mixture was 

 obtained by applying salinities to the mixing 

 equation, S(M, + M,) =M,S, + M,S, where: M, 

 is the mass in the slope water that corresponds 

 to a mean salinity (S,) of 34.85 "/oo As deter- 

 mined from samples in the upper 150 m., M,. is 

 the mass of Gulf Stream water corresponding 

 to a mean salinity (SJ of 36.45 "/oo in the upper 

 150 m.; S is the resulting salinity of 35.55 "/(m, 

 as obtained by computing the mean value of all 

 available T-S curves at the highest points of 

 coinciding properties. The computed proportion 

 of masses was M, = 1.29 M^.., which indicates 

 that a somewhat larger amount of slope water 

 than Gulf Stream was supplied to the mixing 

 process. If all mass separated from the Gulf 

 Stream were to return after mixing, the volume 

 of water returning would be more than double, 

 but such total return seems unlikely. 



EFFECT ON ENERGY IN THE GULF STREAM 



The departure of part of the dense water to 

 the left side of the Gulf Stream below 300 m. 

 would help to maintain the upper 1,000 m. of 

 the water column at a higher density than 

 would otherwise be the case, and the total mass 

 of dense water would also be inci'eased. In ad- 

 dition, the inflow of dense water at the left side 

 of the Gulf Stream should displace lighter 

 water to the right and consequently increase 

 horizontal pressure gradient across the Stream. 

 Thus, a rotation of mass to the interaction sys- 

 tem and back to the Gulf Stream would con- 

 stitute an energy source contributing to the 

 maintenance, and even intensification, of the 

 Stream. It is hardly possible to assess what 

 proportion of the total complex of individual 

 driving and impeding forces of the Stream such 

 a source of energy would represent; too little 

 is known about that complex. It could be ex- 



pected, however, that the proportion, although 

 unknown, would be greatest in the late winter 

 and spring, when temperature and density dif- 

 ferences between Gulf Stream water and in- 

 shore water are large. 



SUMMARY 



Repeated sections along three transects of 

 the Gulf Stream off Chesapeake Bay in the 

 spring of 1963 revealed a process of interaction 

 between the left flank of the Gulf Stream and 

 the adjacent slope water. The data, though in- 

 complete, suggest the following interpretation 

 of the process: 



1. Warm, saline water from the left side 

 of the Gulf Stream was shifted to the left 

 by transient intensified convergence in the 

 slope water-Gulf Sti-eam boundary. 



2. This warm water became isolated from 

 the Gulf Stream by divergence near the 

 surface and by upwelling. 



3. Intense mixing of the separated Gulf 

 Stream water with the slope water gen- 

 erated a dense water type at depths of 

 about 80 to 180 m. 



4. Because of the transient occurrences of 

 unstable mass distribution, a part of the 

 water (a, >~27.0) moved downward and 

 along equal density surfaces and joined 

 with the left side of the Gulf Stream at 

 depths of about 250 to 700 m. Some of the 

 mixed water was probably discharged into 

 secondary streams farther downstream 

 and to the left of the main body of the 

 Gulf Stream. 



ACKNOWLEDGMENTS 



Thomas S. Austin and J. Lockwood Cham- 

 berlin of the Bureau of Commercial Fisheries 

 provided suggestions and critically reviewed 

 the manuscript. 



LITERATURE CITED 



FOKD, W. L., J. R. LONGARD, AND R. E. BANKS. 



1952. On the nature, occurrence and origin of cold 

 low salinity water along the edge of the Gulf 

 Stream. J. Mar. Res. 11: 281-293. 



FUGLISTER, F. C. 



1951. Multii)le currents in the Gulf Stream sys- 

 tem. Tellus 3: 230-233. 



422 



U.S. FISH AND WILDLIFE SERVICE 



