titative in nature and presented the detailed cir- 

 culation features of Hudson Strait which were 

 speculated on by Smith (1937). Campbell's data 

 were obtained during the autumn 1955 and sum- 

 mer 1956 and shows the seasonal influences on the 

 areas. This work provides the complementary 

 data needed to connect the circulation and inter- 

 changes occurring across the entrance to Hudson 

 Strait as found during the subject 1965 expedition. 



The generalized circulation picture for the 

 noithwestern part of the Labrador Sea is quite 

 clear. The oceanographic sections occupied dur- 

 ing the 1965 expedition were specifically designed 

 to describe in detail the contributions of the water 

 masses that make up the Labrador Current and to 

 quantitatively describe the interchange at the 

 Hudson Strait entrance. 



Recent findings as to seasonal and annual varia- 

 tions in temperature and volume flow of the 

 Labrador Current has initiated new thoughts con- 

 cerning spring iceberg threat predictions on the 

 Grand Banks. Fluctuations in the heat and vol- 

 ume transport of the Labrador Current, coupled 

 with the variations in available icebergs during the 

 spring, tend to cause the iceberg threat of one year 

 to differ sharply from another. Iceberg mortality 

 during transit from north to south, particularly 

 along the coast of Labrador, is greatly influenced 

 by the temperature and velocity of the Labrador 

 Current. This is particularly true in the current 

 area west of the swiftest flowing boundary fila- 

 ment, flowing along the shelf break, wliich divides 

 the cold, low salinity water to the west from the 

 warm, saltier water of tlie Labrador Sea. This 

 inshore or shelf portion of the Labrador Current 

 acts as the deep freeze which conveys the icebergs 

 south. "Water properties in this current band are 

 characteristically cold, less than 2° C, and low 

 in salinity, less than 34.0%=. This property com- 

 bination results in lighter water than that found 

 in tlie more saline Labrador Sea and accounts for 

 the boundary or frontal zone which generally lies 

 along the shelf break. These horizontal property 

 differences, between the coastal water and the 

 Labrador Sea, sets up the west to east pressure 

 gradient whicli results in the southward trans- 

 port along the western boundary of the Labrador 

 Sea. Smith (1937) points out that variations in 

 tlie amount of light, low salinity water available 

 along the Labrador coast will cause variations in 

 the velocity of both the boundary current filaments 

 and the inshore water mass that carries the icebergs 



south. Likewise the temperature of this water not 

 only influences the current velocity but also dictates 

 the deterioration rate of the icebergs as they are 

 transported south. An understanding of the 

 origin and control of this characteristic water mass 

 will ultimately allow perfection of ice season 

 severity predictions when combined with knowl- 

 edge of the count of available icebergs which are 

 to be transported south. 



NARRATIVE 



The oceanographic expedition was conducted by 

 the CGC EVERGREEN, a 180-foot buoy tender 

 class oceanographic vessel, in support of the Inter- 

 national Ice Patrol. 



The expedition departed Boston, Mass., on 19 

 July 1965, and arrived at the first oceanographic 

 station (9409) off the coast of South Wolf Island, 

 Newfoundland, on 25 July 1965. The stations 

 shown on figure 1, were occupied in a serial man- 

 ner, terminating on 13 August 1965, at station 

 number 9508 in the center of the southern end of 

 the Labrador Sea. 



Sea ice along the coast of Labrador and Baffin 

 Island offered no obstacle to the survey work. 

 Most of the ice fields encountered averaged from 

 two-tenths to four-tenths and generally the ves- 

 sel's speed of advance was maintained at 10 knots 

 making good the base course. Two heavy fields 

 of ice were encountered where the ice had been 

 packed in strings up to 15 feet thick by the wind. 

 The EVERGREEN was delayed approximately 

 2 hours by these floes which were mostly rotten ice 

 and in general easily pushed aside or cracked 

 apart. Most of this ice was encountered off Cape 

 Dyer, Baffin Island, on the northern most section 

 occupied. No accurate count was kept of the ice- 

 bergs sighted but a gross estimate is that 150 ice- 

 bergs, mostly grounded, were passed and sighted 

 either visually or on radar. 



Oceanographic stations generally consisted of 

 electronic bathythermograph lowerings, Nansen 

 casts, and bottom sampling. One hundred Nansen 

 casts, sixty-nine core or grab samples, and one 

 hundred forty-five electronic bathythermograms 

 were obtained. The distribution of these sam- 

 plings are shown in figure 1. 



Teflon-lined water sampling bottles of the Nan- 

 sen type, manufactured by the Ballauf Manu- 

 facturing Co. or the United Machine Co., were 

 used during the expedition. Temperatures were 

 measured with protected deep sea reversing 



