The Labrador Current, as differentiated 

 from the Labrador Current Water Mass, is de- 

 fined in this paper as follows. At section A2 

 it is the total southerly flow through the east- 

 west leg and the total easterly flow through 

 the north-south leg. At section A3 it is the 

 total southerly flow west of the dynamic trough, 

 and at section A4 it is the total westerly flow 

 north of the North Atlantic Current. Since the 

 above definitions are simple to use and do not 

 require questionable subjective analysis, their 

 use appears justified. 



The total flow of the cold core of the Labra- 

 dor Current as defined by KoUmeyer (1967) 

 was also determined. The volume flow of this 

 cold core, consisting of water less than 2° C. 

 and 34.3%o, is indicated on the time-series plots 

 by a dashed line. On these figures a dashed line 

 is also used to indicate the minimum tempera- 

 ture observed while occupying each section. 



Section A3 is the most interesting time series 

 to examine in detail. Because the southward 

 flow of the Labrador Current between the 

 Grand Banks and the dynamic trough is usu- 

 ally quite well defined, it is also the most 

 accurate. The 12 reoccupations of section A3 

 indicate that the Labrador Current undergoes 

 rather large changes in a matter of days ; for 

 example a change in the volume flow of two 

 sverdrups occurred over 2 days around 25 

 April. The cause of these fluctuations is still 

 open to explanation. Besides the limitations of 

 the geostrophic method, possibilities include 

 tidal or internal wave effects, short-term varia- 

 tions in spring thaw and runoff, variations in 

 the discharge of water from Hudson Bay 

 (Kollmeyer, 1966), variations in the North At- 

 lantic Current, and of course, instrument error 

 or error in the selection of depth of no motion. 

 The general trend of volume flow at section 

 A3 throughout the season conformed to that 

 described by Smith (1937), namely an increase 

 in volume flow between April and May due 

 to a "spring freshet", and then a decrease in 

 June. In 1967 the volume flow attained a record 

 value of over 11 sverdrups on 13 May, and the 

 average dynamic current between stations 9928 

 and 9929 were on the order of 3 knots. Un- 

 fortunately, the CGC EVERGREEN did not 

 reoccupy section 3 just before or after 13 

 May. The wind for the 24 hours previous to 



station 9929 was from the south and averaged 

 14 knots. This opposed the flow of the Labra- 

 dor Current and would have caused an Ekman 

 transport toward the east. Since the geos- 

 trophic approximation does not directly con- 

 sider the wind-driven current, it is possible 

 that the actual flow was less than the geos- 

 tropic flow. The volume flows for 22-27 April 

 and 21-25 May indicate that there are, un- 

 doubtedly, accelerating forces. 



Most of the contribution to the large volume 

 flow came from solenoids between stations 9928 

 and 9929. The T-S diagram for station 9928, 

 figure 30, is somewhat unusual. It shows that 

 the water down to 20 meters was relatively 

 warm and fresh, indicating it came from the 

 Grand Banks. The water between 30 and 150 

 meters was cooler and fresher than normal 

 Labrador Current water at the same depth; 

 however, the salinity is the controlling factor 

 and the water was less dense than normal. 

 Between 200 and 350 meters the water appears 

 to have characteristic temperatures and salini- 

 ties of 1.75° C. and 33.85, somewhat colder, 

 considerably fresher, and therefore, less dense 

 than normal. Instabilities are evident in this 

 depth interval. There was an abrupt change 

 in the water properties between 250 meters 

 and 265 meters. From 265 meters to 415 meters 

 the water was considerably warmer, fresher, 

 and less dense than normal. Below 475 meters 

 the water had normal temperatures but was 

 fresher and less dense. It is primarily the 

 unusually low density of the water below 265 

 meters which caused the high dynamic stand 

 of station 9928. Examination of the T-S curve 

 for station 9929 in the dynamic trough shows 

 that the water was colder and fresher than the 

 normal mixed water type, and that the density 

 was greater. It is this combination of unusually 

 light water at station 9928 and slightly denser 

 water at station 9929 that was the dynamic 

 reason for the large volume flow on 13 May. 



Comparison of the average temperature and 

 salinity in the Labrador Current on 25 April 

 and 13 May, figure 28, shows that although the 

 temperature and salinity were similar on the 

 two dates, the volume flow in May was larger 

 by a factor of 3. The surface dynamic height 

 with respect to the 1,000-decibar surface of 

 the westernmost station, the trough station, 



