After the stations occupied during the second survey had been 

 classified as to water mass, samples of water from a few stations 

 selected as typical Labrador Current water and typical Atlantic 

 Current water were analyzed for total phosphorus concentration by 

 personnel of the Woods Hole Oceanographic Institution. If differ- 

 ences in total phosphorus can be used to trace water masses it would 

 seem that these two water masses, having such widely different origins, 

 might be expected to show characteristic differences if any exist. 

 These preliminary measurements showed an encouraging difference. 

 Since there was very little overlapping range of either temperature 

 or salinity in the two water masses, the concentration of total phos- 

 phorus was plotted against a,. Whereas the Labrador Current water 

 all had about the same concentration of total phosphorus, m the 

 Atlantic Current water samples measured the phosphorus had low 

 values in the lighter water, increased to a maximum at intermediate 

 densities and then decreased toward the steady concentration char- 

 acteristic of the Labrador Current water. The preliminary results 

 were sufficiently encouraging to warrant the analysis of additiona 

 samples collected. This work is now in progress and will be reported 



upon when complete. ■ ■ ^^ 



The water of the North Atlantic eddy is characteristica ly warm 

 and the Labrador Current water and the mixed water are colder, in 

 crossmg from the warm water to the cold water the transition is 

 abrupt and at the sea surface the change is so strikmg that this steep 

 horizontal temperature gradient has been called the cold wall . 

 The melting of ice will of course proceed at a greater rate m the warm 

 water than in the cold water. The location of this transition zone is 

 consequently of importance in determining the bomidary of the area 

 which is ice infested. If, as is the case, this transition zone is not 

 stationarv, the prediction of the location of the boundary of the ice 

 infested ^rea must embody the prediction of the location of the 

 transition zone in depths of the order of magnitude of the draft ot an 

 iceberg. Its location at the sea surface may be different from its 

 location a short distance below the surface and it can be dehneated 

 only by subsurface measurements. To eliminate the more rapid 

 fluctuations at the surface the criterion of the boundary of North 

 Atiantic Current water was taken as the condition that a temperature 

 of 6° C corresponded to a salinity of 34.9 5° /oo- 



In the vicinitv of the Grand Banks this boundary is irregular in 

 shape and to gei a numerical measure of its general advance toward 

 or retreat from the Grand Banks, the area between the boundary and 

 certain fixed rhumb Imes was used. These lines were the 4oth parallel, 

 the 49th meridian and a line from 43° N., 49° W., through 42 N., 

 47° W., extended to the boundary. This area was larger or smaller 

 as the boundary retreated from or advanced toward the Grand Bank.. 

 It was assumed that the position of the boundary was determined b> 



45 



