117 



in the area at the time. The behavior of the ice conforms as might be 

 expected to the circulation as denoted on the map. The distribution 

 of temperature as plotted on Figure 59 plainly shows that warm water 

 previously mentioned on Figure 55 had worked its way to the north- 

 westward along the Bank slope, while on the other hand cold water 

 from the north curled offshore 150 miles or so westward of the Tail, 

 finally to be carried along in a return stream to the eastward, 30 to 

 40 miles off the continental edge. A comparison of this map with 

 the two earlier temperature charts. Figures 51 and 55, shows the 

 development of this rotating movement of the warm and cold waters. 

 The lightest surface water (fig. 60) was in the form of a band 25 to 30 

 miles in width and more or less paralleling the Bank contour about 

 60 miles offshore. The effect of solar warming of the surface layers 

 during the latter part of June is clearly shown by the increase in values 

 for the specific volumes from those collected for May. (Fig. 52.) 



SUMMARY 



The work this year marks the first attempt at dynamic calculation 

 of ocean currents on board a surveying vessel immediately following 

 the collection of the data and also the employing of such informa- 

 tion at once for the benefit of passing ships. The three sets of obser- 

 vations (figs. 49, 53, and 57) permit us to follow the changes that 

 took place in the circulation around the Tail of the Bank from April 

 29 to June 30. First, we may regard the circulation as found by the 

 earliest survey as more or less characteristic of the waters around 

 the Tail of the Grand Bank. On or about May 15 warm salty water 

 from offshore interrupted this scheme of circulation by pushing in 

 toward the southwest slope and pinching off the flow of Arctic water 

 that normally drifts clockwise around the Atlantic face of the Grand 

 Bank. This movement characterizing the currents in May had 

 slackened before the latter part of June, and the scheme of circula- 

 tion had returned to what we regard as normal. Except for this 

 unexplained interruption the cold current continually flowed around 

 the Tail and to a variable^ distance (approximately 150 miles), along 

 the southwest slope where it turned to the eastward, joining the warm 

 current known as the Gulf Stream. This distribution and direction 

 of the currents tended to form a great anticyclonic eddy off the south- 

 west slope of the Grand Bank. 



RELIABILITY OF CURRENT MAPS 



One of the problems upon which we wished to gain information as a 

 result of the season's work, was the rate of change in direction and 

 velocity of ocean currents, to tell whether one survey a month would 

 serve all practical purposes or whether rapid changes in the circula- 

 tion would make more frequent surveys necessary. There have been 



