covered and the number of stations occupied in the Grand Banks region 

 that the June survey is the only one approximating the coverage obtained 

 in a typical pre-war survey. In dividing the 42 stations of the June 

 survey into three groups representing the different water masses no 

 group contains a large enough number of stations to form a very secure 

 basis for the comparison of the 1948 season with other years. In 1940 

 the curve representing the T-S relationship in the Labrador Current 

 water was displaced from that representing the 7-year average for the 

 period 1934-40 toward higher temperature for a given salinity.2 From 

 the June survey of 1948, the T-S relationship in the Labrador Current 

 was found to be similar to that found in 1940. The characteristics of 

 the Atlantic Current water in 1948, as in 1940, were, temperature for 

 temperature, somewhat fresher than the 7-year average. In the typical 

 mixed water only 7 out of 12 stations followed the typical curve, the 

 other five scattering from the typical curve to the curve for Atlantic 

 Current water, and the typical curve in 1948 was similiar to that for the 

 7-year average. 



The existence of a typical mixed water in this area has been interpreted 

 to mean that the basic components, Labrador Current water and Atlantic 

 Current water, mixed in remarkably constant ratios to form the water 

 found at levels below 100 meters, whereas the mixture found above that 

 level was described on a T-S plot by points which scattered widely be- 

 tween the characteristic curves of the two parent water masses. What- 

 ever the system of controls governing the ratio of the components of the 

 mixture, the presence of any considerable number of stations at which 

 the T-S relationship is found to vary from that of the typical mixed 

 water to that of Atlantic Cvnrent water would seem to indicate that those 

 controls were not effective all along the margin of the Atlantic Current 

 water. A plausible interpretation of the observations is that the usual 

 sitviation which gives rise to the typical mixed water is one in which the 

 mixing zone is narrow and active and the horizontal transition from one 

 water mass to another is abrupt with the resulting low probability of a 

 station being located in the mixing zone. The situation in which the mix- 

 ing zone is broad and the transition grachial provides a good probability 

 of stations being located in the mixing zone and the observations from 

 those stations showing a mixture of variable ratios of the parent water 

 masses. Thus in the light of this explanation, the transition from 

 Labrador Currcnit water to the ty[iical mixed water was normally abrupt 

 in 1948 and unusually gradual from the typical mixed water to Atlantic 

 Current watei'. 



In earlier bulletins of this series fluctuations in the Labrador Cur- 

 rent in the Grand Banks region have been discussed with respect to cer- 

 tain sections which have been occupied repeatedly. These sections, 

 called T, U, and W, are located as follows: Section T running south- 

 easterly from about 46°20' N., 49°00' W.; section U extending east and 



2 See V. S. Coast Guard Bull. No. 30, p. 40. 



76 



