magnitude. Scobie and 

 Schultz (1976) substantially 

 agreed with this position. They 

 stated that although the cur- 

 rent direction can be inferred 

 realistically from isopleths of 

 dynamic height, calculating 

 speeds by taking measure- 

 ments perpendicular to the 

 isopleths leads to low esti- 

 mates of the current magni- 

 tude. The current magnitudes 

 calculated from the normal 

 charts approach a maximum 

 of 40 cm/s only in a few loca- 

 tions in the core of the off- 

 shore branch of the Labrador 

 Current south of Flemish 

 Pass. Other studies, particu- 

 larly Wolford (1969) sug- 

 gested that the core speeds 

 were about 50 cm/s to over 

 100 cm/s. Scobie and Schultz 

 (1976) state that these are 

 more reasonable. Also, us- 

 ing geostrophy to calculate 

 currents has several well 

 known limitations, such as 

 assuming a level of no mo- 

 tion and assuming friction- 

 less, unaccelerated flow. 

 The intent of increasing 

 the Labrador Current core 

 speeds was to be conserva- 

 tive in the operational 

 sense. It was argued that 

 it is better to overestimate 

 the southward movement of 

 icebergs toward the shipping 

 lanes than to underestimate 

 the extent of the iceberg 

 threat to safe navigation. 



Page 80 



PREVIOUS CHANGES TO 

 THE 1979 CURRENT FILE 



The first documented 

 permanent changes to the 

 data base were recom- 

 mended by Kasslerand Shuhy 

 (1982). They examined the 

 current values in three re- 

 gions (Figure C-3). In area A, 

 which is bounded by 50 N to 

 52 N and 51-20 W to 55 W, 

 they based their recommen- 

 dations on geostrophic cur- 

 rent calculations from 393 

 hydrographic stations and 

 the drift of one satellite- 

 tracked buoy. The hydro- 

 graphic data included 60 sta- 

 tions taken by a 1981 IIP 

 cruise and the remaining 

 data from the archives of 

 the National Oceanographic 

 Data Center (NODC). Kassler 

 and Shuhy recommended re- 

 ducing the current speeds in 

 A from 23 to 14 cm/s, which 

 was the maximum average 

 geostophic current calculated 

 in the area. With one excep- 

 tion, the current direction re- 

 mained unchanged. That ex- 

 ception was in the area of an 

 observed anti-cyclonic loop 

 centered at 51 N, 52 W that 

 was observed in the hydro- 

 graphic data and the drift of 

 a1 980 satellite-tracked drifter. 

 They stated that the loop 

 was consistent with the 

 bathymetry in the area. 



Kassler and Shuhy 

 also compared drifter trajec- 

 tories from 1 979-1 981 with the 

 currents in areas B and C. 

 They found good agreement 

 in B and recommended no 

 changes. In area C, the buoy 

 trajectories showed a north- 

 ward-flowing current in the 

 area from 47 N to 51 -30 N and 

 42 W to 46 W. They calcu- 

 lated the mean buoy drift 

 through the region and rec- 

 ommended that the data 

 base be changed to reflect 

 these values. At a few, iso- 

 lated locations, marked by 

 X's on Figure C-3, they found 

 some internal consistencies 

 that were corrected. Finally, 

 they recommended the fur- 

 ther use of drifting buoy data 

 as a new source for calculat- 

 ing mean currents. 



Anderson (1983) 

 used 12 buoy tracks to com- 

 pute mean currents in three 1 ° 

 of latitude by 1° of longitude 

 rectangles forthe region north 

 of Flemish Pass (48-49 N, 46- 

 49 W). He made permanent 

 modifications to all of the mean 

 current values in the Ice Pa- 

 trol data base for that region 

 by setting all the values within 

 each 1 ° by 1 ° rectangle to the 

 mean value calculated forthe 

 1°by 1° grid. 



