on the other hand, the volume transport varia- 

 tions were shown to be very irregular. The 

 expression from which these volume trans- 

 ports were computed was derived by assuming 

 that the accelerations were small with respect 

 to the magnitude of the forces acting. Hence 

 an expression for volume transport should be 

 developed based upon the initial assumption 

 that the accelerations are not small with re- 

 spect to the acting forces. 



Figure 68 shows the relationship between 

 the dynamic height values of a Bank station 

 (top line) and a trough station (bottom line) 

 along Standard Section 3. It should be noted 

 that the geographical coordinates of both the 

 Bank station and the trough station vary with 

 time. The Bank station selected had the maxi- 

 mum dynamic height observed and the trough 

 station had the minimum value observed. This 

 maximum value was not the maximum value 

 of dynamic height observed along the section, 

 but the maximum value observed in the west- 

 ern portion. These maximum and minimum 

 values alone were not significant. The distance 

 between the stations must also be known to 

 determine the volume transport changes, i.e., 

 the volume transport values are directly pro- 

 portional to the diff'erence in dynamic heights 

 and inversely proportional to the distance be- 

 tween stations. Recalling the volume trans- 

 ports from Figure 64 or Table II, the largest 

 transport value calculated did coincide with 

 the largest difference in dynamic heights ; but 

 the next largest difference coincided with the 

 lowest transport value observed. The maximum 

 distance between trough and Bank station cor- 

 responded to a moderate transport value while 

 the minimum distance corresponded to a small 

 transport value. This figure indicates that 

 there is very poor agreement between the 

 difference of maximum and minimum dynamic 

 height values and volume transports. This fig- 

 ure also can be used to determine if the trough 

 gradually filled as summer appi'oached. As- 

 suming that colder, less saline water was 

 transported south by the Labrador Current as 

 spring commenced, this water would transit 

 the trough region and manifest itself in the 

 mixed water of the trough. Assuming further 

 that the system is salinity controlled, the 

 dynamic height of the trough stations should 

 gradually increase as summer approaches. This 



is not shown in the figure. The trough dynamic 

 height values gradually decreased, increased, 

 and then gradually decreased with time. 



The uncertainty in station location can con- 

 tribute significant errors to the total volume 

 transport calculations. Bowditch (1962) dis- 

 cussed the factors that contributed to errors 

 in Loran A positions. Stommel (1960) stated 

 that Loran A accuracy under the best cir- 

 cumstances was ±1/4 nautical miles. Adams 

 (1942) stated that a careful observation on 

 one star under the best conditions can give a 

 line of positions correct within ±1/2 nautical 

 miles. He further stated that the accuracy of 

 an individual sun sight under a similar condi- 

 tion was better. Each ship that occupied 

 Standard Section 3 operated under identical 

 navigational instructions. A fix was taken 

 upon arrival and departure from station. The 

 official station position was the arithmetic 

 mean of the two positions. 



Horizontal position determination for the 

 three serial occupations conducted 16-17 and 

 21 April were radar ranges and bearings on a 

 moored buoy. These three occupations were 

 conducted in fog and drizzle with winds up to 

 gale force. The last occupation of Standard 

 Section 3 was conducted at night in fog and 

 light winds and sea state 1. Most position de- 

 terminations during this occupation were by 

 dead reckoning adjusted for drift. The volume 

 transport values presented here are believed 

 accurate to within ±10%. It is emphasized' 

 that this figure represents the maximum limits 

 within which the volume transport values can 

 vary. These tolerances still indicate that large, 

 short-term volume transport variations oc- 

 curred during the winter and spring of 1966. 



STANDARD SECTION 2 



As stated previously, there were three oc- 

 cupations of Standard Section 2. The volume 

 transport information for two of these occu- 

 pations is presented in Figure 69. This infor- 

 mation is also presented in Table III. There 

 was no indication of the dramatic volume 

 transport changes observed in Standard Sec- 

 tion 3. An examination of the dynamic topog- 

 raphy along Standard Section 2, Figure 15 

 and Figures 42 and 43, indicated that there 

 were significant changes between the HUM- 

 BOLDT occupation and the last EVER- 



18 



