THE INTENSIVE SURVEYS: VOLUME FLOW ANALYSIS 



The 1973 Intensive Surveys yielded three sets 

 of oceanographic data in the same location on a 

 relatively fine scale with only five days interven- 

 ing. It is tempting then to analyze these data 

 with the idea in mind of quantifying the rela- 

 tively high frequency, small scale horizontal 

 flow characteristics. The first avenue of ap- 

 proach is to determine and compare the volume 

 transport into and out of what is essentially in 

 cross section a trapezoidal solid constituting a 

 volume of approximately 2.6 x 10" cubic meters. 

 A comparison of the net volume transport 

 through the walls of this body of water (fig. 11) 

 shows the relative change in the direction and 

 volume of flow from one survey to the next. The 

 extrapolated values of section "D" have been 

 adjusted so that there is no flow into or out of 

 the sub-sediment section of the Bank, thus it is 

 a more realistic estimate of the volume flow in 

 this area. Section "C" has also had its extrap- 

 olated values adjusted to agree with sections 

 "A" and "D" in order that net transport through 

 all four sides defining the survey area would 

 total zero. 



Comparison of the First and Second Intensive 

 Surveys 



The results show a nearly linear increase in net 

 transport which was southerly through the top 

 section (A), of 76% from survey I to survey II, 

 and 34% from survey II to survey TIL Figure 

 12 indicates an increase in transport for both the 

 southerly flowing Cold Core and Warm Water* 

 as well as the northerly flowing Warm Water 

 during the interval between the first two surveys. 

 The north flowing fraction of the Cold Core re- 

 mained at a constantly low value. Comparison 

 of the surface dynamic topographies from each 

 survey (figs. 6 and 7) shows a broadening of the 



* Cold Core is defined liy the Ice Patrol Division of 

 the U.S. Coast fiuard Oceanographic Unit as water 

 which is loss than 2.0°C and 34.3V„„ : Warm Water is 



greater tlian 2,0°(" and 34.3V„ 



dynamic trough in the center of the section with 

 a transfer of much of the nortliward flowing 

 water to the east. The result was a 2.33 m^ s"^ 

 rate of increase of net southerly volume transport 

 which compares well with a 2.29 m^ S"^ rate of 

 increase of tlie Labrador Current Cold Core 

 transport. 



There was a dramatic decrease in westerly 

 transport with a less substantial decrease in east- 

 erly transport to yield an insignificantly small 

 increase in net transport (easterly) for section 

 "B" which defined the eastern border of the sur- 

 vey. It is evident from the spacing and number 

 of the surface dynamic height contour intervals 

 (figs. 6 and 7) that the easterly flow through this 

 section was less intense during the second survey. 



The net increase in northerly transport of both 

 Cold Core and Warm Water was slightly more 

 than the increase of the southerly flowing water 

 through the southern section, "C", to give a small 

 excess of northerly flow over that of the first 

 survey. 



Considering the relatively consistent volume 

 transports through the eastern and southern 

 boundaries of the survey when compared with 

 the acceleration of southerly flow in the topmost 

 section, it is evident that the balance must occur 

 in the western section. Indeed this is the case 

 with a 1.438 x lO^m^s' increase in Cold Core flow 

 (westerly) through section "D" which even in- 

 cluded a reversal of net flow from east (off slope) 

 to west (on slope) flow. In spite of the large 

 percentage change taking place on the western 

 boundary, at no place did the geostrophic current 

 speed exceed 13 cm s"^ and for the most part was 

 considerably less. As is apparent from the dy- 

 namic topography the westerly flow is concen- 

 trated between the nortliern two and between the 

 southern two stations of this section. It seems 

 that the rapid rate of increase in Labrador Cur- 

 rent flow could only be accommodated by a flow 

 onto the shelf on the western boimdary since the 

 North Atlantic Current prevented expansion to 

 the south and east. 



12 



