TABLE 4 



Comparison of the 1973 Intensive Dynamic Surveys calculated volume transports and surface cur- 

 rents for section "D" (fig. 1). One series of calculations (Constant Plxtrapolation Values) was 

 derived from a single set of extrapolated temperatures and salinities. The second series (Var- 

 iable Extrapolation Values) used a different set of extrapolations for each section normal to the 

 slope in accordance with the traditional method. 



A. VOLUME TRANSPORT 



For each survey the net volume transport and 

 surface current have been calculated for the N-S 

 slope section. In one case the same extrapolated 

 T and S values were used for all stations — those 

 from the northernmost station. In the other, 

 different extrapolated values were derived for 

 each section. The results show that the net vol- 

 ume transport determined using the variable 

 extrapolated values was overestimated by as much 

 as .87xl0'^m's"' and that the surface currents dif- 

 fered on the average by 81.1% to 115.5% when 

 compared with those determined from the same 

 (constant) set of extrapolated values. Even 

 though the difference averaged only from 

 9.2 cm s ' to 15.0 cm s-\ a reversal in direction 

 was encountered in 42% of the comparisons. 



In the practice of applying the oceanographic 

 data to the Ice Patrol current analysis, upslope- 



downslope flow is not normally directly esti- 

 mated as it has been here for this special survey. 

 However, the surface dynamic heights for each 

 survey are plotted on a chart and are contoured 

 at each 0.02 dynamic meter interval. As a con- 

 sequence of applying different extrapolated values 

 to each section, whatever upstream-downstream 

 slope of T and S properties that exists in the 

 stations adjacent to the continental slope is ex- 

 tended into the Bank and is represented as a 

 slope of the isosteric surfaces below the sediment 

 boundary from one section to the next. The 

 surface dynamic heights, as it has been shown, 

 are biased by this artificial flow normal to the 

 Bank. Often when surface dynamic topographies 

 are contoured from these erroneous surface dy- 

 namic heights of shallow stations, a false flow of 

 significant magnitude onto or off of the Bank is 



10 



