100 



and because of the resulting critical balance between grounding of the 

 bergs in the cold shallow water and the deterioration from melting in 

 the warm deeper water. Thus it will be seen that a shift of the Lab- 

 rador Current in a direction normal to the Labrador Coast will have 

 an important effect on the quantity of berg ice appearing in the Grand 

 Banks region. Such a shift took place in 1939 and is traceable to the 

 departure from average wind conditions along the Labrador coast 

 during the preceding winter. Monthly charts showing the departure 

 from normal of barometric pressure indicated that during the winter 

 of 1938-1939 there existed an abnormally strong off-shore component 

 of winds along the Labrador coast. On the basis of this the ice fore- 

 cast for the 1939 season was qualified as follows: "As the Smith for- 

 mulae consider only transportation under average conditions of tem- 

 perature, it is anticipated that the number of bergs actually drifting 

 south of latitude 48° N., will exceed the above-mentioned figure of 500 

 because the prevalence of off-shore winds along the Labrador coast 

 has probably afforded a colder than usual deep-water path for the 

 bergs and thus reduced the percentage mortality during this part of the 

 journey. For similar reasons it is expected that the east coast of the 

 Avalon Peninsula of Newfoundland will be freer of bergs than is usual 

 during the months of May and June at which season their number is 

 usually at a maximum." Both parts of this qualitative prediction 

 proved correct. 



No opportunity for determining the magnitude of the offshore shift 

 of the Labrador Current was available until the post-season cruise, 

 several months after the winds probably had their maximum effect. 

 Figure 29 shows the temperature section found in the vicinity of the 

 slope off South Wolf Island, Labrador, during July 1939 in comparison 

 with the thermal conditions which were found during July 1938. An 

 inspection of figure 29 shows that the eastern (offshore) limits of the 

 — 1°, 0°, 1°, 2°, and 3° isotherms underwent offshore horizontal dis- 

 placements of 6, 8, 8^2, 8, and 6 miles respectively while the warm axis 

 at 200 meters was 10 miles farther offshore in 1939 than in 1938. From 

 this it will be seen that in the vicinity of the slope similar thermal 

 characteristics were found about 8 miles farther offshore m 1939 than 

 in 1938. In this locality a horizontal change of 8 miles means a change 

 in depth from 370 meters to 940 meters. Differently expressed, the 

 effect of this shift on the berg mortality is to reduce the amount of 

 melting suffered by a berg traveling the same course. The upper 20 

 meters is occupied by a steep temperature gradient with the surface 

 temperature varying greatly from time to time. Considering only 

 depths from 20 meters to 200 meters m a position near the slope, the 

 average temperature of the water column was 0.5° in 1939 compared 

 with 2.0° in 1938 for the same location. Apparently, then, any pro- 

 longed departure from average conditions in the offshore component of 



