lated only forcases when there 

 were three or more buoys 

 passing through the bin. 

 These mean values were then 

 blended into the existing 

 data base using a two dimen- 

 sional least squares spline fit 

 based on HP's current update 

 program (Summy and Ander- 

 son, 1983). 



CHRONOLOGY 



The first efforts, un- 

 dertaken before the start of 

 the 1989 iceberg season, fo- 

 cused on the currents in 

 Notre Dame Bay and the 

 coastal waters near south- 

 east Newfoundland. These 

 are the areas that previously 

 had the mean currents set 

 to zero. Because the avail- 

 able current data are 

 sparse, the mean currents 

 in these areas are not well 

 known. The changes were 

 based on current charts 

 provided in Dinsmore 

 (1972), Petrie and Anderson 

 (1983), and Greenberg and 

 Petrie (1988). The latter is 

 the result of a barotropic nu- 

 merical model. These 

 changes, which were 

 largely subjective, affected 

 fewer than 100 grid points. 

 Most were changed from 

 to 10 cm/s or less and the 

 direction approximately 

 followed the local 

 bathymetric contours. 



Early in the 1989 

 iceberg season (17 April 

 1 989), a permanent modifica- 

 tion to the current data base 

 was implemented that in- 

 cluded all the buoy data col- 

 lected in the offshore branch 

 of the Labrador Current up to 

 that time. The data set is de- 

 scribed by Murphy and 

 Hanson (1989). The most im- 

 portant effect of this change 

 was the reduction of the speed 

 of the core of the offshore 

 branch in the region south of 

 Flemish Pass from 80-115 

 cm/s to 40-50 cm/s. There 

 was very little change in the 

 direction of the current in that 

 region. In this area the largest 

 amount of data were collected, 

 with some bins representing 

 the drift of 10-15 buoys. 



Between the 1989 

 and 1 990 seasons, acompre- 

 hensive revision of the IIP 

 current data base was under- 

 taken using the entire Ice 

 Patrol drifting buoy archive, 

 including the data collected 

 during the 1989 iceberg sea- 

 son. The entire IIP opera- 

 tions area was included in 

 this review, including the 

 areas affected by the 

 permanent modifications 

 made early in 1989. All the 

 grid points that represented 

 at least three buoy tracks 

 were modified to reflect the 

 calculated mean values. In 

 addition to the changes based 



on the buoy data, the current 

 speeds in two areas were 

 reduced. The current speeds 

 on the Grand Bank and the 

 northeast Newfoundland Shelf 

 were changed from 23 to 7 

 cm/s. About 200 grid points 

 were affected by this modifi- 

 cation. The rationale for this 

 change was that the charac- 

 ter of the mean flow in this 

 area is not well known, and 

 that wind effects were likely 

 to be important in the shelf 

 dynamics. Reducing the mean 

 current speed reduced the 

 effect of the mean current on 

 the modeled iceberg drift 

 and allowed the wind-driven 

 terms of the iceberg drift 

 model to play a greater role 

 in the drift predictions. Finally, 

 the currents speeds were 

 reduced in a small area im- 

 mediately to the east of the 

 offshore branch of the 

 Labrador Current from be- 

 tween 50-52 N. About 80 grid 

 points were affected by this 

 change. The new speeds were 

 approximately half those 

 previously shown in the area. 

 This reduction was required 

 because the speeds in the 

 offshore branch of the 

 Labrador Current were ob- 

 served to be half the 1979 

 values. 



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