justment and continuity of flow in the current 

 or the mixed water laying further to the east. 



Figure 13A is a T-S plot of the more westerly 

 stations on the Banks in 1965. The figure in- 

 cludes north-south lines of the first, check, and 

 third survey stations, and two second survey 

 stations which straddle the northern end of the 

 first and third survey lines. Each station is 

 represented by a point determined from the sta- 

 tion's average salinity and average temperature, 

 the use of which are permitted by shallow depth 

 and homogeneity of the water. The stations 

 taken on each of the separate surveys are con- 

 nected by lines for clarity. Although these sta- 

 tions are not centrally located on the Banks, they 

 are representative of the Banks water slightly mod- 

 ified by the swifter flowing current to the east. 

 The salinity of the water on the Banks during the 

 third survey (stations 9353 to 9403) has been re- 

 duced by about 0.2%o from the first survey (sta- 

 tions 9238 to 9296). As expected, the water is 

 warmer to the south because of warmer air tem- 

 peratures. 



The stations occupied during the second survey, 

 numbers 9342 and 9343, whose locations match 

 stations 9296 of the first survey and 9352 of the 

 third, show that the low salinity water had already 

 arrived at the northern end of the Grand Banks 

 when the second survey was made. On the check 

 survey, the salinities of stations 9301 and 9302 

 fall nicely between the first and third survey sta- 

 tions of similar location, stations 9255, 9256 and 

 9373, 9391 respectively. Salinity decreases were 

 observed at both stations while mean temperatures 

 remained about the same. A period of only 9 

 days separated the check survey stations from the 

 first survey stations, however, the salinities had 

 already lowered by half of the total change foiuid 

 during the third survey, 7 weeks after the first 

 survey. 



The above findings tend to indicate tliat the 

 pronounced water characteristics indigenous to 

 the Labrador Current in tlie spring, arrive rather 

 abruptly. This is also supported by the volume 

 flow data from tlie check survey. This is contrary 

 to previous beliefs that gradual temperature and 

 salinity changes take place during the early 

 spring and that the changes w liich occur in tlie 

 current system occur over a period of months. 

 Rather, it is apparent tliat tlie time scale of change 

 is more on the order of 1 to 2 weeks and perhaps 

 less. 



Circulation Response 



The abrupt changes in water characteristics and 

 dynamic heights that occurred on the Banks and 

 slope were in response to the arrival of the colder, 

 less saline water from the north. It is reasonable 

 to conclude that because these changes occur on 

 the Banks and slope first, a certain period of lag 

 is to be expected prior to the arrival of this water 

 in the trough area. The water in the Labrador 

 Current must circuitously flow down toward the 

 Tail-of-the-Banks before its arrival in tlie trough 

 area. As pointed out above, the dynamic height 

 of the trough area during the three surveys 

 showed a gradual increase in elevation. Figure 8A 

 shows that although an abrupt change had 

 occurred in the dynamic height of the Banks and 

 slope water between the first and the check 

 survey, the trough station on the check survey 

 changed little in dynamic height. Conversely, 

 the Banks station on the third survey changed 

 little from the check survey while the trough 

 station exhibited a considerable change. This 

 leads to the conclusion that the low salinity 

 water observed in the main stream of the Labrador 

 Current during the check survey had not had suffi- 

 cient time to complete the trip to the trough area 

 and influence the water type there. However, on 

 the third survey significant changes in the water 

 properties above 400 meters occurred. Figure 

 IDA indicates these temperature and salinity 

 changes which occurred in the trough area during 

 the survey intervals. Between the dates of the 

 check survey and the third survey light, low 

 salinity water arrived at the trough. The effect 

 was to raise the elevation of the trough and thus 

 reduce volume flow. 



If section U is examined over a year (figure 14A), 

 limited correlation appears to exist between the 

 change in mean salinity of the Banks' water and 

 the volume of water flowing south. An exact 

 correlation cannot be made here because of the 

 influence of temperature on the water's specific 

 volume, the time lag, and unknown mixing 

 proportions which tend to modify the elevation 

 of the water in the trough area. This is evident 

 from the volume reduction that occurred on the 

 third survey even though tlie Banks station 

 decreased in salinity and liad a higher dynamic 

 height. If the check survey had not been con- 

 ducted, the rapid rise of volume flow would not 

 have been observed and the portion of figure 13A 

 for 1965 would have looked hke that for 1964. 

 This kink in the volume flow curve for 1965 



