OCEANOGRAPHIC CONDITIONS, 1973 



Three oceanographic cruises during the periods 3-26 April, 

 8-29 May and 13 June - 14 July were conducted by the U.S. 

 Coast Guard Oceanographic Unit in support of the International 

 Ice Patrol aboard USCGC EVERGREEN (WAGO 295) . Approximately 

 13 days of the final cruise were devoted to special surveys 

 that provided field data and verification to a Labrador 

 Current model, developed by Commander Ronald C. KOLLMEYER, 

 USCG. Salinity and temperature data were collected to a depth 

 of at least 1000 meters (bathymetry permitting) using a 

 Salinity-Temperature-Depth (STD) Sensor System. Data were 

 recorded on magnetic tape using a digital data logger for 

 further processing upon return to the Coast Guard Oceano- 

 graphic Unit, Washington, D.C. From processed data, charts of 

 dynamic topography of the sea surface relative to an assumed 

 1000 decibar level of no motion were constructed (figures 

 22-27). Only the 7-22 April and 1-4 July dynamic topography 

 charts show the prominent features of the general circulation 

 pattern on the Grand Banks. The Labrador Current can be seen 

 slowing southward along the eastern slope of the Grand Banks 

 near the 1000 meter depth contour. To the east is a dynamic 

 trough separating the colder Labrador Current from the opposite 

 flowing North Atlantic Current. 



The April survey (figure 22) shows the dynamic trough just 

 east of the Labrador Current separated into two dynamic lows 

 as a result of the North Atlantic Current, an interesting 

 phenomenon not shown on the average or normal dynamic topography 

 for the month. This intrusion lessened the velocity of the core 

 of the Labrador Current in the vicinity of 45°N to less than 

 half its normal of about 35 cm/sec, yet at 150 kilometers north 

 and south of this location, average velocities were determined. 



The survey area in May as shown in figure 23 was apertured 

 with anomalous dynamic highs. Associated geostrophic currents 

 exceeded 50 cm/sec in the vicinity of 45°N 48°W where a 

 dynamic trough is normally located. Evidence of a portion of 

 the Labrador Current is present on the southeast corner of 

 the Grand Banks, however, its presence further north along the 

 1000 meter contour is weakly defined at best. The North 

 Atlantic Current in the eastern portion of the survey area 

 was approximately in its normal location. Its velocities 

 approached 100 cm/sec or approximately twice their average 

 values. 



