83 



course being no greater than that of the titration method used in 

 calibration. 



The current maps prepared during the season as well as the map 

 showing current conditions on the post-season cruise were made fol- 

 lowing the procedure used in the past several years, the season's maps 

 being referred to the 1,000-decibar surface and the post-season map 

 being referred to the 2,000-decibar surface. 



Figure 20 shows the current map resulting from the first survey, 

 made between March 30 and April 8. This map shows several strik- 

 ing abnormalities. Both the strength and breadth of the Labrador 

 Current along the eastern slope of the Banks are unusual and even in 

 the absence of an exact knowledge of the volume of flow involved can 

 be said to be responsible for the considerable southeastward extension 

 of the cold mixed water tongue which, defined on this chart by the 

 971.1- dynamic meter isobath, reaches to about 41° N., 48° W. 

 This tongue of cold water was a characteristic of the 1939 ice season 

 and its extent as shown in this figure, in spite of the fact that the 

 Atlantic Current is seen to be flowing with unusual strength unusually 

 far north for this time of year, indicates the abnormally large volume 

 of flow of the Labrador Current immediately preceding and during 

 the period of this survey. Other notable features of figure 20 are the 

 early development of the Grand Banks whorl and the comparative 

 freedom of the current pattern from irregular meanderings. 



The dynamic current map resulting from the second survey, made 

 April 23 to May 2, is shown in figure 21. In this figure the general 

 pattern of the preceding survey is recognizable, but many changes 

 are to be noted. The northward thrust of the mixed water on the 

 left-hand side of the Atlantic Current north of latitude 44° N., had 

 moved westward toward the Banks about 30 miles. This apparently 

 blocked some of the southward flow of low dynamic height, forcing 

 the southeastward bulge of the contour lines in the northeastern part 

 of the map. This southeastward intrusion of colder water was no 

 doubt assisted by westerly and northwesterly winds during the inter- 

 val between surveys. The great strength of the Labrador Current 

 found in the first survey was still in evidence and one of the results of 

 this continued flood of Labrador Current water was the widening and 

 further extension of the tongue of cold mixed water which in the first 

 survey reached to about 41° N., 48° W. Another result was the en- 

 croachment of Labrador Current water on the shallow waters of the 

 southern end of the Grand Banks. At the southwestern corner of the 

 map a complicated current pattern was found and while the available 

 observations are open to more than one interpretation, it seems certain 

 that the corner station was located in a mixed water pool which had 

 become detached from the main body of mixed water to the eastward. 

 Whether from a decrease in the strength of the Gulf Stream or from 



