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correct and that the section did cross the Gulf Stream and a portion of 

 that branch which recurves toward Bermuda. 



Investigation of the vohime of flow past this section was undertaken. 

 As described in Bulletin No. 27 of this series, there is evidence that 

 the depth of the motionless surface is greater beneath the Atlantic 

 Current in the vicinity of the Grand Banks than beneath the Labrador 

 Current and that this depth is about 2,000 or 2,500 meters. Accord- 

 ingly, the investigation of the volume of flow past this section was 

 based on a reference surface of 2,000 decibars. A velocity profile 

 was constructed and the volume of flow computed by the numerical 

 method was checked graphically by planimeter measurements on the 

 velocity profile. The eastward transport past the section amounted 

 to 58.6 million cubic meters per second, of which 21.7 million returned 

 westward past the southern part of the section between stations 2715 

 and 2713. This large eastward volume of flow substantiates, as does 

 the depth of the 10° isotherm (820 meters at station 2715), the 

 opinion that tliis section completel}^ crossed the Gulf Stream. It is 

 of interest to note that the eastward-moving water was transferring 

 heat at the rate of 760 million cubic meter degrees Centigrade per 

 second at a mean temperature of 12.96° C. 



It is characteristic of the northern border of the Atlantic Current 

 that the upper layers are more uniform, vertically, in temperature 

 and salinity in that part of the current of higher dynamic height (right 

 hand) than the upper layers in that part of the current of lower 

 dynamic height (left hand). Because of the nonlinear relation be- 

 tween temperature and density it has been noted that adiabatic mix- 

 ture of water masses of difl'erent temperature-salinity characteristics 

 results in a greater density than the mean density of the masses before 

 mixture. Thus if a storm passes over an area having the temperature 

 and salinity distribution described above, and if that storm mixes 

 the upper layers of the different parts of the area uniformly, it will 

 result theoretically in the lower dynamic heights being lowered more 

 than the higher dynamic heights are lowered and the surface velocities 

 being increased by the resulting increase in gradient. Now it is also 

 characteristic of the northern border of the Atlantic Current that 

 the less uniform upper layers of the left-hand side of the current 

 have a steeper vertical density gradient than the more uniform upper 

 layers of the right-hand side. It is qualitatively known that the 

 effective depth of mixing produced by a given storm is much less in 

 surface layers of high vertical stability than where that stability is 

 low. This conservation of water-mass identity by vertical stability 

 results in selective mixing which will reduce the differential lowering 

 of the lower dynamic heights which would be produced by uniform 

 mixing and might even reverse the effect and produce a decrease in 

 the horizontal gradient of dynamic height. The writer is not aware 



